I highly doubt there are any cases where the player didn't want to leave, at all, and the coach *forced* it to happen. That seems to be what is implied here by some, but if I'm wrong about that then I'm wrong.
Every player who enters the portal, at least, has some non-zero percentage of wanting to leave their current situation on that team.
To my gut feeling, granted having 0.0 inside info (take what you will from supposed expose pieces on blogs), Fleck seems like a kind of guy who would tell a player at worst "look if you want to stay here and stay on the team, you won't get any playing time and you won't be further developed by our coaching staff, but that is your decision and we'll honor your scholarship ... just know you're hurting your teammates by taking that scholarship away from us by choosing to not transfer or medically retire."
If anything, the medical retirement route seems like a great gig for guys who don't want to leave the U but won't have a chance to contribute on the field. But my wild guess is that most players would rather try to find another opportunity to play somewhere else.