I would guess separate pedals for the brakes would be for stunt driving. If you’re flying along, and lock up the rear brakes, you can bring the back of the car around quickly, punch the throttle, and take off in the opposite direction.
First time I saw this happen was in 1979. I was 18 and hanging out with a buddy of mine in a nearby town. There were a couple of nice looking girls he knew riding around in a Pinto Cruizin Wagon. She’d fly down a vacant side street at night, pull the hand brake fast while keeping the button held in, so she could release it quickly, bring the car around and floor it. The girls were underage, wanted us to buy beer and go riding around with them. We passed on that - nothing but trouble in our eyes, but they put on a good show!