I think he didn't nerf them on purpose, just to balance it out. As they were insanely good in melee and this time he wants it more equal.
I DO think he may be a tad sexist with the argument about the representation in the series.
Technically speaking, there were no new female fighters in Brawl and I'm very surpised my personal favourite Krystal wasn't included despite being high on his poll and beating out some characters who got a few less votes.
Wolf's popularity was basically nonexistant on that poll and I was shocked, but meh, I like them both.
I think next time round, he should buff up the female side of the roster as well as the villains too.