I may rattle a few feathers here, but just because the guy bowled 900 does not mean he is a great bowler. I do not know, but he could have bowled his 900 on a walled shot, and the difference on that night was that he carried.
Just because the guy's average is not real high means nothing. #1-like was already stated, it could have been a sport shot average. #2-many of us have had nights when we pounded the pocket the entire night and maybe had a high 700 series or even an 800 series and all that may have kept us from that were a few solid 8's or 10's.
If someone bowls 850's and only 2 8 pins, flush, were left does that mean that he/she didn't throw the ball as well as any of the guys that shot 900 did? I don't think so. In order to throw 300 you have to have some luck, let along bowling 900. To bowl a 300 you have to have every shot carry, maybe you tripped a 10 pin late, or an 8 pin was the last fall. The pins have to fall, once you have released the ball properly, hit your mark, and had the proper ball speed...it is all up to the pins.