I think TikTok is pretty strict with censorship. 9/10 times when I see something like this it has a TikTok logo in there. Dunno if it would actually consider diagnosis a "bad word" but maybe people just don't want to risk it..?
I mean there's a fairly big amount of people talking about mental health disorders on TikTok. Many of them self-diagnosed. TikTok might well be trying to crack down on people talking about these things.
Jeez people are getting lazy these days: not cropping screenshots, leaving misstaps in the middle of the image... It takes half a second to press undo >:((