It's not, because the comparison was about brand value and brand perception. YC and Harvard have a very similar elite only-the-best-get-in-and-then-you're-set perception in their respective markets (plus a scarily similar "if you know guys who knows guys, it'll be easier to get in" aspect).
They're more similar than dissimilar. For example, both try to have a selective process where they try to gauge potential of applicants, and whether they're worth investing resources into. Universities are actually a specific subset of accelerators..