The difference is it legal to fire someone for using TikTok. It’s just not believable, which makes it clear that the firing was illegal (discussing wages is one of the few things you can’t be fired for).
edit: so maybe, I guess, to defend against the argument that they were fired for salary disclosure?
Exactly, if you fire the only black guy on the team for wearing a blue tie but other people wear them as well it could be argued you lied about the reason.