Surely it depends on the course in question I know that physics at birmingham didn't have any clearing places and most people on my course have above the AAA entry requirements. However I do know that in other subjects there were a lot of places left but I think mainly because the university didn't plan well for the changing circumstances.
However I do see where your coming from that what you would call the "RG1" haven't had to go through clearing. I'm not quite sure which unis you would say make up this category but I guess you would say Oxbridge, imperial, LSE?
I can see where you are coming from and I too think there should be a movement of entry requirements in the coming years especially if there is a continuing grade deflation. However I do still stand by the fact that there are still fully subscribed courses at your "RG2" unis. Possibly because they have a more diverse range of degrees some not as popular as others.