As he faces the throwing area out of the back, his left arm as you said should be countering his throwing arm, instead he has it extended forward in front of his body which causes an imbalance/ wobbly axis. He's basically blocking his body/ hips from rotating smoothly into the center which is why his finish is a bit wonky. The young man has the right idea out of the back and if he fixes what we've both stated he should show even more improvement. 😉
As he faces the throwing area out of the back, his left arm as you said should be countering his throwing arm, instead he has it extended forward in front of his body which causes an imbalance/ wobbly axis. He's basically blocking his body/ hips from rotating smoothly into the center which is why his finish is a bit wonky. The young man has the right idea out of the back and if he fixes what we've both stated he should show even more improvement. 😉