Also worth mentioning that the notion of different Starfleet crews wearing different uniforms at the same time was nothing new either: the Antares crew in "Charlie X" wear The Cage/WNMHGB uniforms when they meet up with Kirk (who is wearing the standard Enterprise variant).
IMO the best explanation is
that Starfleet is just loose with the uniform code.
Yes, and it makes sense for the majority of cases.
...then, you've got stuff like, Picard critizising Ro Laren for wearing her beloved ear ring - which btw is a cultural expression. So, Worf is allowed to wear his sash but Ro isn't?
..Ok, I agree, you can say that Picard wanted to troll Ro because she was such a misfit.
But are there any other cases where someone gets criticised because of things like that?