I must be seeing something different, I see you fire a shot then stand by the same fence post you fired from as you reload then move off slightly for another angle to fire your second shot?
Rule303 has obviously been there done that, it just ain't as easy as cranking another round from the magazine of a bolt gun while on the move, or for that matter if things really go south, getting another round up the spout if fallen to the ground. You haven't got a hope in hell of achieving that with a double.

But if facing a charging dangerous animal at close range I would definitely appreciate a double with two sure shots, bang bang flop dead hopefully. As a matter of having fun to prove a moot point yes go for it and have fun, I just don't see these comparative speed shots between a double gun and a magazine bolt gun under very calm and controlled conditions as being relevant to field conditions considering the situations these dangerous game guns often enough find themselves being used.