First off, some really interesting responses here.
To play devil's advocate for a bit, I completely understand the outrage, but, before we criticize let's walk a mile in their shoes. If any studio has the right to make this claim, it's the studios behind a behemoth like AC. They're on a yearly release schedule and that shit needs to be done, polished, and as bug-free as possible. Above all they have to make sure the thing's finished first, and, all things considered, playable females are just extra animations and voices.
Literally every game ever made has to cut some feature for lack of time and resources even though everyone has been pushing for it, and, even though it would be the right thing to do, a great inclusive feature, and win them some good PR, it's not an unreasonable call to cut the female characters because they couldn't spare the extra weeks (thanks for that reddit thread that helped clear up how much time it takes for development). It's easy for Jim to fall back on his rhetoric of "they think we're fucking stupid", which is definitely part of his outrage shtick, but the fact is that the publishers know that the general public IS absolutely ignorant of these issues. They simply won't notice, and drawing a few days of heat from us gaming enthusiasts is a small price to pay. They WILL notice if Unity is a broken, buggy mess like AC3 was.
Assuming it would actually make the overall game experience worse (and whether or not it does we will never know), I choose polish over crowd-pleasing inclusiveness, though it may not be popular to say. It's why I've spent so much more time with GTA than Saints Row. Instead of seeing females added into AC Unity at the last minute, I'd prefer another really fantastic, well thought out AAA game with a fleshed-out female main character to pick up the torch from Bioshock Infinite and Last of Us. It would be more meaningful than slapping boobs on a hooded assassin you'll never get to know anyway.