True, but the events of season 1 and NEXT still follow the novels to an extent, even if they move things around. I'm hoping Revolution does the same, which is what the information so far implies they're doing.
When you say something is 'based on' something, that doesn't mean it will be an exact copy. How many movies based on books, comics, games, etc ever follow it perfectly? Even Lord of the Rings and Harry Potter in movie form don't follow the books perfectly.