I think it is just the camera angle and the motion in general. I actually always wanted to try this, but can't manage to get my hand backwards. I haven't been actively bowling recently, though.
Awesome job again and you should throw up more records of "trick shot" games. Maybe if I can ever get the funds to bowl as much as I used to again, I can try to break some. :)
The amount of torque on your hand must hurt after a while. I know of some people who do this as their primary bowling style, it looks really natural for you, oddly.