That side arm throw is becoming more and more common and obviously Mahomes does it better than anybody else, but I saw it trickling down into the high school ranks my last few years coaching. Sometimes when you try and change those mechanics it gets worse and also creates too much thinking, when you want your QB progressing through his reads. I would try and tweak mechanics early if my QB's were rough, but if it became apparent it would not help I would let them play and focus on things like reads and better alignment of the lower body in relation to the throw. Jake has been working with Beck, if I am not mistaken and his group will make the most out of what he has.