Mistwell
Crusty Old Meatwad
What does it mean to say that something is "not fantasy," then?
It means you are aware when you are introducing a non-fantasy element into your fantasy game. For example, the authors of Expedition to the Barrier Peaks understood they were introducing science elements into the fantasy game when they wrote up that material from Metamorphosis Alpha for 1e D&D. It was done with a purpose, and an acknowledgement that they were elements which were not usual to the fantasy game. That awareness informed their choices, and it helped the Players and DM approach the material. They knew the perspective would be, "What happens when characters from a fantasy background come into contact with elements of a science fiction background?" That "otherness" was the whole point. The science wasn't just "another aspect of the fantasy realm", it was clearly different from the fantasy realm and therefore interesting for it's unique presence there.