No your take is very interesting. For most films the costume designer does take things like this into consideration especially if they have a good relationship with the director. FYI Gwyneth's clothes were all by Donna Karen. Not sure Ethan and Ann's though sorry. I watched Pretty Women again recently and afterwards read up about the clothes and everything she wore was made by the costume designer. None of them were by a designer name. She had to fight the film makers to let the opera dress be red. I can't imagine it any other colour.