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.
For Oryx and Crake and sequels, it's hard to argue that "a novel with no robots or spaceships ... but a whole lot of genetic engineering" isn't actually SF.
It doesn't pass the test that e.g. a novel set on the actually existing International Space Station does. It does contain a core fictional scientific "what-if" extrapolation.
I respect the author's opinion here and I hold a different opinion, for that reason.
But that then begs the question… isn’t Margaret Atwood already the first SF author to win the Booker Prize? Making Harrison second?