Exactly.
The technique shown on that site worked fine on my first car, which was a plymouth with about a one mile gap between the pedals. On every subsequent car, including my x subbie, my vette, the FSAE car at Maryland, and the Rotus, I "heel" and toe by placing the ball of my foot on the brake pedal, then using the outside of my foot to blip the gas pedal.
You have to adjust your pedals so when you press the brake pedal to the point that it gets firm, it's even - or slightly raised - relative to the gas pedal, so that it's easy to blip the gas pedal.
Does it make a difference, HELL YES. You can downshift without upsetting the balance of the car at all. On a car like mine that has alot of rotating mass in the engine, downshifting without heel and toe can really upset the balance of the car when under heavy braking