I don't have a strong personal opinion on this, but the PG essay mentioned in the comment you link to advises people not to start a startup while in college and to do other things in their "early 20s", while Early Decision is targeted specifically at people who are currently college students and (mostly) in their early 20s. I don't think there's a 'gotcha' there, but there is at least a tension, no?
While you're correct that the comment you're responding to is a bit sloppy in summarizing what PG said ("20s" instead of "early 20s"), its basic point still makes sense.
YC is not the Church of Paul Graham, so I don't see any need to dive into Pauline exegesis and attempt to reconcile YC's current admissions process with everything PG has ever said. YC can do what it likes, and people can note what may or may not have changed since PG was in charge of it.
The early decision is for people who want to start a startup once they finish college. I don't see a tension between that and advising people to finish college.
The difference between "20s" and "early 20s" is huge; it's the difference between Google and not-Google (btw, that pg essay includes this information). Since not-not-funding-Google is, to a first approximation, the entire startup investment business, conflating the two is more than a bit sloppy, and the GP comment (imputing an inconsistency to PG that doesn't exist, with cynical implications), makes no sense once one adjusts for what pg really said. He's been consistent about this for many years! I'm being irritable again now though. but not with you!
You made me laugh with the Pauline bit!