it seems like some type of health issue.
they haven't been using him, but also didn't cut him, which tells me they don't want the bad PR from cutting a dude going through some shyt.
might be concussions, maybe something heart or some other internal organ related due to his weight.
just pure speculation but those are the only things i can think of that would keep you out and have them being secretive about it. if he tore something or broke something they'd just come out with it imo.
anyway not having Vince book him like shyt is probably a good thing for his career and value in the long run, especially if he can secure a release and go work somewhere else.