Well, I'm living proof that you can get a bid as a junior at UGA and I certainly don't "walk on water."
I knew going into it that there were several houses I wouldn't get very far in and that was okay. It wasn't anything personal. I'm not saying I agree with it though. In my experience, sophomore and junior pledges were some of the most dedicated members while a lot of freshman dropped out or didn't make grades.
I think the soph and junior quota idea is great!