Quite true, the only thing indisputable is what's actually shown in the show. And so far we have no definitive proof there that goes one way or the other.Though the the inconsistency of Spike referring to the time when they saved the Crystal empire as "the last time we were here" in Equestria Games bugs me. As it which would imply that they were never there for the events of Equestria Girls if that was true.