I don’t buy that. A significant number of people around the world have heard of Harvard, while I doubt that most people in the U.S. alone have heard of YCombinator. I’m yet to talk to a friend or family member about this place without having to explain what YC is. Nobody has to explain Harvard.
Not to say YC isn’t a big, impressive brand that draws talent, just that it’s still orders of magnitude from the top of the Ivy League.