When most of the show hinges on ONE hand-waving bit of magic, tough to state anything else with certainty. Just as easy to say that it's just the DEAD ones that don't heal, and if you had this OTHER magical strain / partial immunity, it works differently.
Since we don't know much about it one way or the other, the subject doesn't exist in real life to make statements about, and we've been shown things that don't quite add up, hard to definitively say right or wrong. Except to the REALLY stupid guesses, of course
I mean, what's YOUR definitive statement based on? Where's your source on how, uh, 'smart zombies' behave?
Not saying it's a thing, just that since they've carefully avoiding addressing the subject, hard to know for sure how things really work in this world.