Wouldn't the recoil spin him around like a top?
I’ve fired while rappeling, but never while traversing which is what the guy in the photo you reference is doing. While rappeling down head first, you are actually braced by your controlling hand such that the recoil has almost no effect.
The recoil of an AK is pretty light and probably wouldn’t spin a 170lb man. Remember, they’re not weightless like in space.