Of course he didn't, he said something worse. The literal quote from Bill Gates is: "But I read mostly nonfiction because I always want to learn more about how the world works".
The immediate conclusion that you can take from that is "if you want to learn more about how the world works, then don't read fiction". It's the assumption that fiction has value only as entertainment.
I'll give you just one example of the opposite. If you want to learn how people in the past thought and viewed the world, then an excellent way is reading the popular fiction of that time. Bonus points if you get to know how they read it.
>Sorry, but it does. Easily testable hypothesis; go to the NY Times Bestsellers lists and compare, book-for-book, what can be "learned" from each (as most of us understand "learning").
Sorry, but if you get to redefine things in order to suit your argument (the word learn), then you are right by default and there can't be any discussion. I won't follow you there.
I know there are excellent non-fiction books that teach you lots of things. But the reverse is true, there are garbage non-fiction books that teach you nothing.
For example: read "Confessions of a Heiress" by Paris Hilton. It's non-fiction, so by your logic, you will surely learn more about the world reading that than something like "1984" by George Orwell, right? Give me a break.