A cop buddy of mine told me of how he learned about the "gangsta style" hold in the early 1990s.
They had the shootee. They even had the left handprint of the shooter on the kitchen door, plus his muddy footprints going a little ways into the room past the door, then turning around and going out. They even had the likely trajectory for the shots. Everything pointed to that door.
But they had a problem. They couldn't figure out how the hell the casings landed about ten feet to the LEFT of the door in the breakfast nook, instead of landing on a counter to the RIGHT of the door.
It took one of the rookies back at the station house, listening to them talking about the case, to come up with the explanation. She mimed pointing a gun at a wall.
Then she rotated her wrist 90 degrees to the left and asked, "Hey, what if the shooter was holding the weapon sideways, like they do in those rap videos?"
My buddy said that everyone else was looking as if lightbulbs had just switched on inside their heads. Every last one of them just could not imagine holding a pistol like that. It took some kid from the MTV generation to explain things to the old farts.
i suppose it could be useful in a quick draw from condition 3. or maybe if you're in a driveby and don't want the casings hitting the back window.