Indeed, you are correct. Most long games usually go down to the final prize. Donks don't happen as often anymore due to EX Pokemon with large HP and other basic Pokemon with over 70 hp as starting. A donk is when you kill your opponents active on the first turn when they have no benched Pokemon.
Deck outs can still happen, but most experienced players will use a supporter called "N" in the late game to prevent this from happening, however it can still happen.
What I was implying with my first post was if he's not taking all of his prizes, then that's probably a reason why he is not winning XD