It's not that, it's more that there are words in general that TikTok does not tolerate, and there's no definitive list of those words. Some of them: gun, pissed, penis, vagina, any swear word, etc.

So since there's no definitive list and you can't make one because the content is not outright deleted (algorithm just ignores it), you end up in a situation where TikTok users self-censor just in case.

This is similar to what China does internally, but the list is definitely different.