He may not be a photoreader, but from all of his intense yet playful study, he probably has a high reading speed or speedreading(maybe). I think the essential part of his knowledge and ability to win was his curiosity and confidence, his scope of interest combined with study brought him a depth of knowledge about many different topics. Since Jeopardy tests so many areas, his wide scope of interest helped him learn more.
Like Paul has said, letting your mind be playful and being interested in the information helps so much with learning that if you posess this then even with reading skills below photoreading, you absorb all you learn, while some photoreaders discard information because they didnt care to remember it.
If you apply photoreading to books that teach a certain skill, chankawo, then you will learn it faster simply because photoreading helps you read that book faster. or, with direct learning, learn and apply a skill quickly. Photoreading is a million times better than not photoreading, by any standard.
