he's got a stomach condition that causes his stomach to fall to a lower place in the abdomen than other ppl. Its a rare condition, called grastroptosis.
Bcause the stomach goes lower it can expand more bcause the diafragm isn't limiting it from above.
He's not skinny, he's athletic, he does lot of exercise to burn all the calories. He's under 10% body fat which occurs in big athletes (average in non-athlete men is about 10-20%), and his muscles have changed into bigger and heavier and faster metabolism to consume more fat and faster due to all the exercise!
Not being fat also means that there's no big fat belly pressing the stomach and preventing it from expanding. That's smart! :)
That allied to a good technique, it's a winning combination.
