We actually don't know if he can or can't because he never tries, but Greene shot 30% from 3 last year and Kier shot 37%. Greene scored 2 more 3s than Kier did, but had 25 more attempts. Miller had a better shooting percentage from 3 than Greene did, but he took almost no attempts (18 versus 114) so I don't think that translates over a full season to anything. Also, if Hartwell is going to start, I'm guessing he'll find Kier when he's open.
But like I said, Hartwell, Kier, X, AJ, Calixte doesn't mean Greene doesn't start. If AJ beats Mar out for the 4 and Greene beats Miller out for the 5th starting spot, I have no problem with that. Certainly, you're going to want Greene's FT shooting in end of game situations.