Exactly FS. With the glut of underclassmen in this draft someone is going to drop to 21 that some staff had as a top 10 player, but Thompson does not.
Also, (I believe) most people think that a GMs draft board is sequentially ranked like Kiper or McShay or whatever, but we know Thompson and other GMs rank players in groupings. @21 Thompson will have more than 1 guy he likes at that pick. If they are all there when GB is on the clock he will likely trade down (partner willing) knowing he can still get one of his guys.