Just give TikTok a phony IPhone password.
You think the software can’t tell it’s phony?
I suspect what's going on is that TikTok is trying to access user data on the phone that, after the latest Apple update, requires the user to authorized that access, by entering the phone password.
And so entering a phony password will not work; access won't be granted, it will prompt again until either the real password is entered, or the user Cancels out.