Yeah, the key distinguisher for "Science Fiction" is that it asks a "What if?" question. Some SF authors (e.g. Margaret Atwood) don't like that because they're writing novels with no robots or spaceships, but too bad, you don't get to choose how other people experience your work.

But that then begs the question… isn’t Margaret Atwood already the first SF author to win the Booker Prize? Making Harrison second?