I'll ask again: isn't it possible that he's right? There seems to be general consensus that girls do not get into computing science at a young age. So it makes sense there would be shortage of women with right ability at the right time for YC. There's nothing controversial about that. And short of inventing a time machine there isn't anything PG can do about that.
I know a lot of women in computing and almost none of them started as young as my male peers. These women code and some started their own companies. But they didn't do it in their late teens or early 20's because they hadn't even discovered it then.
You don't need to mold someone from adolescence in order for them to be a founder or a hacker. It's not something you have to grow up with.
PG is in the business of spending very small amounts of money on in the slim hope that a few of them will be wildly successful and return hundreds of times on that original investment in a relatively short time frame. He invests in people who move to the valley and live huddled together on peanuts and ramen. Those young people are a very small and specific subset of all people who can be founders or hackers.
But Otherwise I agree with you entirely.