Talking about it in this way is like saying that YC has made a profit on every company that successfully exited. It's technically true, but it tells you absolutely nothing about the performance of Y Combinator as a whole.
A while ago I read an interesting article about why the US and Canada are so different in culture. Unfortunately Googling failed to find it again, but the summary version was that the US was heavily influenced by immigration by Ulster Scots from Northern Ireland, where Canada was more influenced by immigration directly from Scotland.
The difference between a colonising culture (the Ulster Scots) versus a colonised culture (the Scots) apparently explains the huge culture rift.
It was a compelling narrative, but that just makes me suspicious about it. It's easy to convince people of your pet theory if you make it into a good story.