Not useless at all.
Slide your left foot over the "tunnel", and use IT to control the brake while you're using the right foot for the HST pedal. Us fluent 3 pedal (manual transmission) car/truck guys & gals will have an advantage with this.
Years ago when I worked for JD, my and another "tech" (also an idiot) were messing around in the shop. I was on an HST JD 4300 I think it was, and decided to try the "cutting" brake. Well I learn't that you can put the HST in high gear, throttle wide open, mash one brake and steer and you can do a stationary burnout on a tractor. Very dangerous, though. There's no telling where the tractor's going to go. Luckily for us, the slick shop floor was wet and it was an oily/greasy spot right there so it was mostly effortless like on ice, but if it were to "catch"? NO telling...probably go through the building, and just on the other side of that wall was the boss' office....THAT would've been hard to explain. Both to the police, the attorneys, AND to the boss....
As said up top, it's easy.