I don't know Fernando Aguilar but is the reason he's 6D not that he's capped at it before becoming professional? IIRC when I played in SF bay area (probably all of USA in the AGA), you couldn't get higher than 6D(7D?) without becoming a pro. I think in tournament lineup you would see something like Mr. A 6D (7.2) where the 7.2 was his estimated rating but it was a long time ago.