I can *almost* see some point in it if you rolled around prior to the draw. We had to do something similar in hand to hand training, make yourself dizzy and disoriented before engaging, and I suppose that might be the theory here. Sure seems like you could do it without the gun in your hand if that's true, and if the plan is too really combat egg roll...well, you lost me.
It is nice of you to give the benefit of the doubt, and the guy is clearly a skilled "operator" but in one of the knife videos he did it was obvious that this is a move he feels gains you something. You are thinking of it in the terms of upping the stress and getting some disorientation and then still performing? We have done that in FOF where it is a valid training tool though I am not sure an actual somersault is required.