The only thing he did was not have a 'follow-through' with his arms after releasing the ball.
It's the sort of throw that at any level will have players screaming for it, but I can't see what was done wrong.
But there's probably a point where this type of throw does become foul...eg when he practically drops the ball a couple of cards in front, or some such, so there's a point where spirit of the law comes into it as well. Just highlighting discussion.