Look, I'm not trying to hurt your feelings. The things you previously listed weren't exactly screaming endorsements of the guy, nor were they very indicative of his actual play... prototypical size and speed doesn't necessarily mean he's going to play like Hakeem Nicks... take Laurent Robinson for example. Prototypical size and better than prototypical speed-- didn't do much for him for the majority of his career.
Anyway, back on topic. I've read the scouting reports but I just don't see the speed with this guy. He seems 'clunky' for lack of a better term. He seems to be slow in and out of his breaks, doesn't possess breakaway speed, doesn't possess many skills running with the ball either. I'm not saying that he's awful, but I just don't see anything he does better than Austin or Bryant.
Maybe the slower speed of the big XII never necessitated the need to play at a higher level, but I just don't see it with Williams. Hope I'm wrong.