You're not paying close enough attention... in this most recent revising of the rankings, Levy Adcock, the OT from Oklahoma State, has dropped from a 2nd or 3rd round prospect to a 7th rounder on their board... Chase Minnifield, the CB from Virginia, was at one time rated in the low 20s by them, now he's 45th... Akiem Hicks, the mammoth defensive lineman from Canada, has come from way out in left field to a solid 6th round grade at this point... NTs Hebron Fangupo from BYU and Nicolas Jean-Baptiste from Baylor have gone from undrafted rookie free agent grades in the 300-400 range to a 5th round grade for Fangupo (142nd overall), and a 7th round grade for Jean-Baptiste (244th)...
Those are just a few players whose rankings have changed dramatically in the last week, off the top of my head...
I've been a fan of that sight for some years now (well, actually I'm a fan of NFL Draft Scout, which is the source for CBS' ratings), and one of the things I've liked best about them is the frequency with which they update their rankings, once the college season begins... they do it more often than anybody else that I've found does...