To be fair Stewart was likely talking more about wearing a uniform all the time like he did on TNG. Not that he would avoid them for a scene or two if needed like a flashback or so. I think he was likely more open to that than say Tom Welling who refused forever to put on Superman's tights.
Nah, he did say “no uniforms” at first, meaning no uniforms at all. However, he has never been someone who can’t change his mind - he very quickly did just that when he realized that some scenes would not have worked as effectively if he hadn’t been in a uniform. He himself has said that the whole “no Starfleet uniforms at all for me plz” thing was a bit presumptuous on his part, lol.