The same can be said of anyone that drives with their foot constantly poised above the brake or touching the brake. And unless you know when you will need to brake in advance, that is what you have to do to gain an advantage. And if you do have some warning you can do the same thing by coming off the gas peddle.

If I were drafting in a race and riding inches off someones bumper I might use your system, but for driving around town or highway driving it is no slower to come off the gas and hit the brake than it is to come off the floor board with your left foot and hit the brake. Also for most drivers it removes the possibility of braking causing the right foot to press on the gas peddle, or of riding the brake.