To me, the most interesting thing about the John Amaechi book isn't his sexual orientation, but his frank admission (via Steve Sailer) that he didn't like playing basketball and didn't try very hard at it. "I respect the game of pro basketball. I just don't think it's all that important. I wasn't going to be embarrassed by Jerry Sloan because basketball had a proper role in my balanced life and I didn't blindly worship a game he made pretty much the entirety of his existence." Or, later in the book, "Why does the performance of so many players decline after they sign multiyear guaranteed deals? It's a little thing called human nature. Plenty of guys - Karl Malone and John Stockton are the obvious examples - play hard no matter how much they make. Other guys lack the discipline. Predicting which player falls into which category is the key to scouting."
This connects to something we've discussed before -- the number of people who have the baseline physical characteristics necessary to be an effective NBA center is vanishingly small. This creates an unusual situation where people can get paid millions of dollars to play that role without being especially committed to doing it well. 6' 4" men are reasonably rare, but also common enough that they're only going to get to be NBA players through fanatical devotion to the game. A really big guy, though, can make it at least marginally without even enjoying basketball. You also get intermediate cases like the frustrating Brendan Haywood who seems to be someone who realizes he can continue to make millions for years and years as a mediocre center with an inconsistent effort level.