You should be disagreeing. Ferguson likes to put prospects into unnecessarily small boxes.
When I look at a prospect, I look at how intelligently and effectively they move, since that's the key to everything on both ends. I can usually make an assessment pretty quickly by watching just a few games, and it doesn't usually change unless they show something completely new and different down the road.
I'm not convinced that Wallace is an above-average starter at the PG spot, and depending on the team that drafts him, he might not be a starter at all. If you look at other tough, defensive-minded PGs--guys like Jrue, Marcus Smart or Terry Rozier, for example--they're much more dynamic as shot creators. They're better at creating separation and attacking defenses off the dribble. The way Cason plays would be fine, if he were 6'5", but I think he's going to come out closer to 6'3". He's not going to be able to bully guys and get by them. He's not going to be able to make plays over the defense. He's probably going to be used off the ball a lot in an offense that really moves and shares it.
The way the Jazz play, where a lot of creation comes from the wings attacking, then Cason Wallace can play off the ball, knock down open shots, and not be at the center of the action. So there could be a fit there. I'd just be reluctant to take Cason in the lottery, unless he fits a role that the Jazz envision at the 1.
I don't see the upside that would make him a high lottery pick. I think he's the guy you take in the mid-teens.