Oh, so it's not that their mechanical cell implants (in this case, in Ichika, who I think is limbless of either one or two legs originally) cannot recover, but conversely, regenerates independently from any injury...
So it's unclear whether Ichika's legs failed to properly respond because of her originally being (in theory) limbless or because she's clumsily legitimately tripped on the stairs.
What we learned though is that,
because this experiment is secret, the fact that their bodies can heal on its own, if exposed to the public,
the memories of the parents of this experiment and the fact that their children have been saved will be erased, thus made to believe that they died in that accident.
While the children will remain under supervision for the experiment, but never seen again by the parents.
There are several possible side effects that can't be prevented, but none are clearly revealed to us the audience from the document.
If any of those side effects are revealed to the public, the children will be subject to "internment", meaning locked in the labratory's "prison" to be left concealed from the public.
As for the event of this chapter:
Both Haruta and Izumi head to Ichika's care. Haruta shudders to the sight of blood spilling off Ichika's head, so Izumi tells him to call the ambulance, while he notices her previous injuries of this morning healed.
Ichika's mother worried sick arrives to the hospital where Ichika is at... to which director Mitsuba and superior Kozuki arrive as well to Ichika's Mother's shock.
I believe it's safe to logically assume that because they're close to work, that this hospital is most likely part of their jurisdiction. Which was revealed to us through Mitsuba that only hospitals that are affiliated with their company is allowed.
I also believe and think it's obvious that the mention of means to erase memories is a hint to ReLIFE, including the fact that they're in the same universe, because Yayoi Sou's last manga: Blue Hearts was also in the same universe by revealing characters from one or the other manga as background characters.
So, it'll be confirmed for certain whenever we see one of the characters from her other manga as background characters.