I think it's more along the lines of his general demeanor and actions in all situations. Throwing his hands up after a bloop hit. Showing frustration when he doesn't get a strike call. Getting upset and then getting hammered when he tries to over throw a fastball. Cursing in anger when his teammates don't make a play.
Not talking to the media is just another thing in a long line of actions that show he may lack the mentality required to be a successful starting pitcher. He is only 24, so I'm sure there's a lot of room to mature, but he certainly seems to lack the mental fortitude that's usually associated with quality MLB starting pitchers.
