I think he is above 50%, which given many are Kane-like drives with no foul contact, is acceptable.
The timing may seem poor, but I don't think it is being overly critical to comment on how a talented, but one of the least efficient players the past few years, can become better. No one is saying he isn't a big part in our success. His defense and ability to give us physical size has been big. Minus his inability to buy a call, his finishing is a big boost off the bench, and his ball-handling as a post is needed for a team short on that skill in the backcourt.
Both his effective and true shooting %s go down with his 3P%. He is a capable driver. If people are running at him as much as the "spacing" proponents suggest, then he should have no problem driving.