Too funny ! Wasn't that sideways shooting actually a spin off from what was seen in room clearing by the Israli special ops ? Armed with a FA machine pistol they did that to compensate for vertical muzzle climb. Start at one side of the room and allow the climb to sweep from one side to the other
while maintaining elevation. I read that somewhere on another gun forum some years ago.
I don't know if its true or not but it did make sense. I rented a FA Glock 34 once at a gun range and it was very uncontrollable with my small hands even with a three shot burst .