So is apple. Just because it’s generic doesn’t mean it’s not protected by trademark law. Trademarks are also first come first serve, exclusive to a given industry (so you could call your company Apple or X, but it better be not in a business where it’s already trademarked). They’re also use it or lose it, and you basically have to sue others using it if you want to keep it.

Obviously the logo isn’t just the character X, it’s a character X in particular font. If they used the same one they would be violating their trademark.