"April - Female Founders, June - General, July - Black and Latino Founders"
I find it somewhat unusual that the open office hours are segregated. Why not just reach out to those groups but have general open office hours?
I'm guessing that this is a serious question, so I'm going to give it a serious answer. This is a classic economic signalling behaviour, akin to getting a college degree in order to signal your intelligence or giving gifts in order to signal your wealth.
Consider two possible YCs: YC(a) is serious about having female and minority founders at office hours, while YC(b) is just trying to be politically correct. Advertising "we encourage female and minority founders to apply" wouldn't cost anything. Advertising "we will only accept female / minority founders in these months" in contrast has a cost -- they lose the opportunity to meet truly awesome founders who do not belong to the appropriate group -- but for YC(a) that cost is partially balanced by the fact that they're spending time talking to members of groups which they would like to help out. Thus the net cost for YC(a) is lower than the net cost for YC(b) -- just like getting a college degree takes less effort for someone who is highly intelligent than it does for someone who is less intelligent -- and so YC communicates to founders that they are more likely to be YC(a) than YC(b).
(Whether anyone thought it through to this extent, I don't know. But people routinely engage in signalling behaviours without being aware that they are doing so.)
YC(a) is serious about being politically correct, while YC(b) merely cares about appearing to be politically correct.
Political correctness is common to the two cases for the simple reason that YC(a) would inevitably help wealthy, well-connected female and black/Latino founders to the exclusion of, say, poor, less-privileged Asian founders. It's hard to explain this behavior in humanitarian terms, but it's easy to explain in political terms. Nobody gets in trouble these days for expressing the sentiment that we need more women, blacks, and Latinos in tech, no matter how rich and well-connected they may be.
The only other possibility I can think of is that YC(a) genuinely wants to help especially deserving founders, and such founders are so overrepresented among women and blacks/Latinos that specifically targeting those groups achieves the goal well enough for YC's purposes. In other words, the cost of reaching such founders may be so much lower when targeting specific self-identified groups that it's worth the minor cost of helping the occasional privileged member of one of those groups. Still, it's hard to avoid the observation that this policy is generally aligned with political correctness, which would appear to justify some skepticism.
(My guess is that YC's policy isn't Machiavellian in the least, but it works adaptively because of a political environment in which explicitly helping women and blacks/Latinos is strongly favored both by custom and by law.)
I think that's true in California, but politically correct favoritism that ignores class helps fuel right-wing extremism.
Perhaps I see that more clearly because I don't live in the SV bubble.