In the words of Brett Brown himself"
"He's really just scratching the surface to what ultimately he is going to be when we start talking about high level of finishing efficiency, growth of a free throw, the rebuilding of his shot, a comfort level of making and shooting an 18-foot jump shot, those things are still on the horizon,” said Brown, a former Spurs assistant who witnessed that program's ability to markedly improve a player's jumpshot.
I think half the problem is he's so ambidextrous and doesn't really know which hand to favour.