I don't see anything at all about this to indicate he did it on purpose.
Maybe you should actually watch the video. He looked back directly at his coach, TWICE, then smacked him right in the face.
I honestly can't imagine how anyonne with eyes would think that wasn't intentional.
Edit: after rewatching, he not only takes two looks back, he then turns his head directly at the coach, AS he is swinging the stick at his face.