I don't know if this is the intended behavior or not, but most of the time, when you're healing a unit that's bleeding, you can't heal it when it's not bleeding anymore (you get the message "can't perform action : unit is not wounded"). However there are a few times where you can heal a unit that is not bleeding : the healing action works and restores HP. This is possible usually once or twice before you get the message "can't perform action : unit is not wounded" again.

I guess it should not be possible to heal a unit that is not bleeding. Or there should be an intermediary state ("hurt and not bleeding but healable") that should be visible on the UI (with, let's say, a yellow portrait instead of red or green, and a yellow "wounded" icon).