I agree with these suggestions. Perhaps, I would add the little knowledge about Chinese legislation and the market, which is quite different from other parts of the world. But I think it would be interesting, thinking strategically, YC attracts more Chinese and thus better know the market.
I'm not sure about this batch, but there has definitely been YC companies in the past with Chinese (and HK) founding teams, and based in CN/HK. 9gag, for example, is HK based. I'm also personally an investor in a S15 YC company with mainland Chinese founders.
* VC money is more accessible for Chinese startups in China
* Chinese startups are mostly targeting local market
* Visa issues?
(these are all wild guesses)