Why does the brake enter into it? When you leave from a stop at an intersection with an auto equipped vehicle, are you putting your foot on the brake to make it go?
Most autos will move the rig on flat ground and as that grade changes to where the rig will no longer move forward, all it takes is a very slight increase in throttle to either hold it in position or begin forward movement. The brakes don't enter into that at all just like you don't need to apply the brake to leave from a stop at an intersection.
It only looks the same, it is not the same. There is a vast difference between holding position on an obstacle and moving slightly forward, back, and changing how the rig is behaving on an obstacle to see if it is going to be in trouble or whether a successful traverse is possible.