I got another flaming torch to throw. I just realised that the current descriptions of fail forward sound awfully lot like forced railroading. As long as the players roll high, they are ensured agency in that everything go as they hope.
However, roll low, and the GM has to introduce something that changes what the entire scene is about. And this has to not match what the players was intending. The GM forcing the game to be about something else than the players were striving for sound awfully close to the definition of railroading to me? In this case it is the rules forcing the GM to do it, and it is only momentarily. But I do not know if that makes it much better?