Where I am, a long time ago, it was a unwritten rule to leave people on medical leave employed. Then I suspect when they are back at work maybe they would be let go. Back then I never knew anyone in this situation. I do know a few that were fired while on leave in the past few years.

But with how the US medical system has pretty much transitioned from non-profits to profits, I doubt there can be any argument saying doing this is OK. Money now talks more than it did years ago.