V & A is a totally different dining experience and is in a class all its own and is not looked at as a signature dining restaurant but a fine dining restaurant and the only one that WDW has.
Being rated number one is by guest feedback of their dining experiences and it is measured internally based on their scores. As for signature there is only 5 signatures ( Citricos, California Grill, Narcoosses, Yachtsman Steakhouse, and Flying Fish). They are truly signature restaurants. And of the 5 Steakhouse is on top for now in Guest eyes or opinion, not WDW staff so it is significant for future guest to know that.
Everyone has their own opinions on restaurants and service just like everything else in life.