One potential flaw I've noticed with Tatum's shot is that he doesn't necessarily get it off the quickest. Many times he doesn't put up threes off of the pass due to having a slower shot, which I think is partly due to him having such a high release and advanced iso game that hasn't forced him to quicken his shot at all.
That's why I wonder how he'd do in the three point contest. His form is virtually flawless, and he's very consistent with it; however, I'm not sure that he can get through the racks quick enough to really challenge to win it.