This doesn't come to me as a surprise to be honest. For those of us who were around from the beginning, and went on the forum, you'd know how much complaining was done just to get the core female characters into the game.
Ever since this game came out it had a heavy bias towards male characters. Even when female characters started coming out, more of them ended up being limited time, or premium. It was always extremely annoying and odd to even male players.
The only thing I can hope for is that they release a super hero event part 2 with all female characters to even out the playing field.
Overall though a feminist could have a field day with this game, easily calling it sexist. I suppose that wouldn't bother the creators too much, because it's not the worst thing the simpsons as a whole has done.