A cousin of mine is abysmal to drive with as a passenger. He follows too closely to the car in front of him, regardless of lane / speed. He will slow down, follow closely, and then aggressively pass. Repeating ad nauseam.

No smooth maintaining of speed and nice passes as able without slowing down.

Surprisingly, his accidents have mostly seemed to involve gas pumps, barriers, and other obstacles at low speed.

I believe inattentive driving correlates more with accidents than things like hard braking, and might be the leading cause of hard braking too (inattentive driving will lead to following distance being reduced too as you are not watching for traffic well ahead and to the side of you).

At the same time, passing on regular intercity road can have the risk reduced (up to a point) by making the passing quicker, by spending less time in the oncoming traffic lane ("aggressive passing"). It certainly does not help with comfort, though.

So perhaps your cousin is a very attentive driver who drives aggressively? That might still only make him an "average" driver (I've had such drivers almost get others in an accident in front of me), but I think it's a balance that needs to be struck, otherwise most would tune out and not be ready for emergencies.

This is left lane driving policy. I am like this, and I was not at first. What makes you drive like this is rush hour traffic. "Move up the lane or move out of the lane" is the sentiment, basically. As others have noted, it is essentially an adversarial process. If you drive nice, people cut in front and you're unable to drive nice to both those behind you and in front.

I don’t think what you’re describing is quite the same thing.

At least I hope not.

More concrete example:

He will be going 65 mph in slow lane. Come up on a car. (Left lane empty). Slam on his brakes. Follow them at 50 mph for 1-3 minutes <1 car length.

Pass, flooring it, if he stays in the left lane he’ll keep going until he now tail gates a car in front of him- usually with large speed variances.

The amount of traffic on the road doesn’t matter. It can be 3 cars and he will drive this way.

I’m not talking about trying to drive through major city rush hour traffic.

Letting them "cut in front" is good driving.

If you have to keep significantly slowing down to get the gap back, that's perfectly nice to the people in front of you but it's not nice to the people behind you.