When I was in college, a 'natty' referred to a far, far different drink. But then again, I did my undergrad at Flyover State U. On the other hand, I bet 80%+ of those folks own a house right now.
I'm pretty sure "natty" means Natural Light and/or Natural Ice at every college. Except maybe some of the rich-kid fallback private schools in the East that most people have never heard of. There, maybe not.