Perhaps. The way he throws looks like he's trying to "steer" the ball to 1B which is usually a sign of confidence. Perhaps it's also the injury - if it is hurting him, he probably should throw sidearm.
It's not an "if", it's been widely reported that throwing is painful and he's been experimenting with different styles trying to find a way that doesn't hurt. So does he lack confidence, of course, but the real cause is pain from the surgery and his lack of practice at alternative throwing styles.