He's not flailing his arms too much that I can see. Also, it seems like he will have no trouble riding switch later on
But what he is doing basically seems to me like a version of falling leaf down the mountain. Only on heel edge, no actual turns, just twirling around. Posture problems that I notice are that he's keeping his legs straight all the way and he seems to be hunching over a slight bit.
Now, I'm still a bit of a newbie myself (maybe intermediate by this point), but I can tell you that lessons will probably help him a lot, both in skill and confidence. (not that you need telling, I reckon...)