It appears to be just the lack of proper external rotation that makes it look funky, although I'd need closer video to tell. Try having him train his rotator cuff, but be careful not to overdo it.
Here's the deal..
What happens at the end of his delivery is primarily the result of what happens with his legs in the beginning. As others have mentioned, I'd recommend he works on his lower half and everything before his arm is involved and then see what is looks like.