I sure hope that Disney explains this to people over the phone. not that I plan on eating at one of these dress code eating places, but for those who wish to do so I think Disney should at least explain this over the phone at the time of booking.
Now for the restaurant in France at Epcot that is a signature dinning place. But I don't think there would be a dress code at that place. I can't say for sure, but think about it this place is in Epcot a theme park where lots of people love to wear Tee-Shirt's so I don't see why Disney would make a business casual dress code at that place. I am sure lots of people would not wish to bring a change of clothes with them to eat there lol. But to make sure always call I guess. I myself will not eat at any restaurant in Disney or anywhere else if I have to wear business clothes. I mean it's great if people want to go to these eating places where everyone is dressed up, but it's just not for me. I like to wear my Flower the Skunk tee-shirt's and jeans