Every single case of recovery to date, irrespective of the methods used, has been achieved by helping people to spend more time in an upright posture. Electrical stimulation is being heralded as a breakthrough in restoring function that exists after the stimulation has ceased.
It is thought that intact nerves are used to re-route messages and receive them past the damaged spinal cord.

No one is considering how gravity acts upon the nervous system and brain, and yet if we remove gravity by compensating with a centrifugal force in orbiting the Earth (microgravity), our cerebro-spinal fluid functions abnormally, squashing the brain against the top of our skull. https://www.statnews.com/2017/11/01/astronaut-brain-changes/ and causing permanent damage to sight, along with a huge range of degenerative problems. Clearly gravity is of paramount importance in balancing and driving the circulation of csf.

It is also interesting that NASA and others have found that bedrest and head down bedrest affect the body and no doubt csf function in the same way that micro-gravity does in astronauts. This article also states that the brain goes back to it's normal position after weeks / months of being back in a 1g environment.

Study unveils changes in the brain during extended missions in space
MEDICAL UNIVERSITY OF SOUTH CAROLINA
http://academicdepartments.musc.edu/newscenter/2017/nasa_Roberts/index.html

 MUSC neuroradiologist Donna Roberts, M.D., conducted a study titled “Effects of Spaceflight on Astronaut Brain Structure as Indicated on MRI,” the results of which were featured in the Nov. 2 issue of the New England Journal of Medicine.

"“Exposure to the space environment has permanent effects on humans that we simply do not understand. What astronauts experience in space must be mitigated to produce safer space travel for the public,” said Roberts."

While living and working in space can be exciting, space is a hostile environment and presents many physiological and psychological challenges for the men and women of America’s space program. For example, NASA astronauts have experienced altered vision and increased pressure inside their heads during spaceflight aboard the International Space Station. 

Roberts suspected subtle anatomical changes in the brains of astronauts during spaceflight might be contributing to the development of VIIP syndrome, based on her earlier work. From 2001 to 2004, Roberts led a three-year NASA-funded bed-rest study, collaborating with other life sciences researchers at the University of Texas Medical Branch in Galveston. A South Carolina native, Roberts had just completed a two-year neuroradiology fellowship at the University of California, San Francisco.

For this study, she examined the brains and muscular responses of participants who stayed in bed for 90 days, during which time, they were required to keep their heads continuously tilted in a downward position to simulate the effects of microgravity.

Using functional MRI, Roberts evaluated brain neuroplasticity, studying the brain’s motor cortex before, during and after long-term bed rest. Results confirmed neuroplasticity in the brain occurred during bed rest, which correlated with functional outcomes of the subjects.

As Roberts evaluated the brain scans, she saw something unusual. She noted a “crowding” occurrence at the vertex, or top of the brain, with narrowing of the gyri and sulci, the bumps and depressions in the brain that give it its folded appearance. This crowding was worse for participants who were on longer bed rest in the study.

Roberts also saw evidence of brain shifting and a narrowing of the space between the top of the brain and the inner table of the skull. She questioned if the same thing might be happening to the astronauts during spaceflight.

In further studies, Roberts acquired brain MRI scans and related data from NASA’s Lifetime Surveillance of Astronaut Health program for two groups of astronauts: 18 astronauts who had been in space for short periods of time aboard the space shuttle and 16 astronauts who had been in space for longer periods of time, typically three months, aboard the International Space Station. Roberts and her team then compared the brain images of the two groups of astronauts.

Roberts and study investigators evaluated the cerebrospinal fluid (CSF) spaces at the top of the brain and CSF-filled structures, called ventricles, located at the center of the brain. In addition, the team paired the preflight and postflight MRI cine clips from high-resolution 3-D imaging of 12 astronauts from long-duration flights and six astronauts from short-duration flights and looked for any displacement in brain structure.

Study results confirmed a narrowing of the brain’s central sulcus, a groove in the cortex near the top of the brain that separates the parietal and frontal lobes, in 94 percent of the astronauts who participated in long-duration flights and 18.8 percent of the astronauts on short-duration flights. Cine clips also showed an upward shift of the brain and narrowing of the CSF spaces at the top of the brain among the long-duration flight astronauts but not in the short-duration flight astronauts.

Her findings concluded that significant changes in brain structure occur during long-duration space flight. More importantly, the parts of the brain that are most affected — the frontal and parietal lobes — control movement of the body and higher executive function. The longer an astronaut stayed in space, the worse the symptoms of VIIP syndrome would be.

Roberts compared these findings with a similar medical syndrome experienced by women called idiopathic intracranial hypertension (IIH), which affects young, overweight women who present with symptoms similar to VIIP syndrome: blurry vision and high intracranial pressure with no known cause. A common treatment for IIH is to perform a lumbar puncture, whereby CSF is drained using a needle placed in the lower back —  a procedure performed by a neuroradiologist such as Roberts. Presently, there is no protocol to perform a lumbar puncture in a microgravity environment."

I have written to the people involved in the recent sci breakthrough using electrical stimulation and as yet have not received a reply.

I suggested that they could greatly improve the outcomes of their research by combining IBT with their upright exercise and mobility programme. 

More Evidence for upright posture effects on spinal cord injury

"Dr. Alberto Esquenazi, the chairman and chief medical officer of Moss Rehab of the Einstein Healthcare Network in Philadelphia, agrees. He screened fourteen subjects, completed training for ten users of ReWalk, and determined that some users reported “improvements in pain, bowel and bladder function, and spasticity.” His study also determined that users “improved their physical endurance” with “no significant adverse side effects” and were willing to use the system on a regular basis." 
https://www.newsweek.com/israel-wheelchair-paralyzed...

Evidence of paralysis from sleeping on a flat bed.

“Just six weeks ago, Jessica Shainberg, 15, woke up with no feeling below her waist.

"She was very calm," her father, Jeff Shainberg, told ABC News. "I didn’t believe her at first, [I said] 'You gotta wake your legs up and we got to go to school.'"

Days earlier, Jessica had felt tingling in her legs, but after a trip to the emergency room, doctors found no signs of anything serious and sent her home, Jeff Shainberg said. But now they family was headed back to the hospital.”
Teen Who Woke Up Paralyzed Now Walking and Running Again

“It turns out that one day, at the ripe, young age of 25, you can wake up from a rather unpleasant dream you were having, roll around in bed in your Brooklyn apartment and curiously, not be able to move your legs.

For me, that was Sunday, March 31st, although as I would later mention to a multitude of doctors, nurses, students nurses and physical therapists, I started feeling what I think were related symptoms the day or two before.”
I woke up one morning and couldn’t move my legs – This Happened to Me – Medium

“medical mystery
Tabitha Fung, 35, has since forged a new career as a wheelchair tennis champion

It was the moment that would have destroyed most people's lives.

Marketing executive Tabitha Fung, 35 and from Rowley Regis, woke up to find she was paralysed from the waist down.”
Doctors baffled after woman woke up paralysed in medical mystery

One night 11 years ago I went to bed after a perfectly normal day and woke up paralysed from the waist down. I tried to get out of bed and nothing happened.
Dad who woke up paralysed from the waist down reveals how MS changed his life