Chalam - great video- this is an example of savant. probaly not using any more of the brain than anyone else just making better use of parts of the brain, using it differently, usually due to compensation because of a damaged area.
It doesn't negate the fact the don't use all of our brain. Its like saying I have a Ferrari, but I never take it past 70MPH. It doesn't mean I only use 10% of the car, I just don't use it to the maximum. I use all the components, the gears the engine the controls etc. But, If however there was an emergency and I had to get a famly member to the hospital I might use it in a different way and drive as fast as I could because the circumstances are different.
The savants brain in effect, has a change of circumstance to the norm and that has helped him to use part his brain differntly. Everyone uses that part, it's not vestigal in me or you, we just don't use it in the same way as the savant.