Miguel cotto hook?

[cocobeware]

I was watching a video of Miguel cotto training,This was when he was still with his old amature coach and I had noticed that he had started throwing his left hooks a little different,So I assume it's something from his amature days.

At first I thought he had just started turning his hooks over a bit better but whem I pause the video he is actually landing almost with the back off his hand.

If you pause it at exactly 0:48 you will see


Anyway just wondering if anyone can tell me what that's about..? Maybee it's due to the shape of the bag,But I thought it looked kinda weird.