So assuming your door was open for some reason, he'd have to reach between you and the steering wheel, reach the retention holster on your right side, extract it from the holster, release the safety (assuming it was engaged), unwedge himself in order to point the barrel at you, and then fire, all the while you're struggling to prevent him from doing any of this?
Not trying to be argumentative. You're the first person who's posted, as far as I know, who has any idea how this works, and I'm curious, particularly since the ME said there were no signs of a struggle.
I think his point was that the officer had to use his weapon and couldn't just fight it out hand to hand because a guy that large might well knock him cold and then could get his weapon and use it on him or others.
All this bs about "unarmed" teen etc ignores the fact the freakin' guy was 6'4" and 300+ pounds. His fists were deadly weapons. He gets his arms around your neck, game over. He gets you on the ground and mounts you, lights out. Trained MMA fighters get the crap beaten out of them in that situation by guys their own weight. Try it with a guy double your size.