I suspect he knows as much. At least, from other writings, he seems to be self aware.

But you have to remember that his business depends on raising money from people that must buy in to the myth that he does have that special ability to spot a winner on day one.

Ironically though, successfully making people believe that you are able to pick winners actually does make the people you pick more likely to win. Being selected by YC not only allows you to raise truckloads of money more easily, it also gives you a boost when making connections or deals with other companies, hiring the best talent, etc.