I'm surprised that the article made no reference to the overlap between Fantasy and Sci-Fi. As much as I hated it at first, I now agree with how book shops tend to merge them - for the most part they are one and the same. The Dragonriders of Pern would be a (very dated) example of how a fantasy book can actually be a Sci-Fi book in disguise - and would have been a much better example in the Science Fantasy pool.