Earlier quoted context omitted.
That's inaccurate. SF/Fantasy contains elements which are not possible under the laws of physics, not anything imaginary. Literary fiction is also imaginary, but taking place in "our world". (The lines get blurrier when talking about imagined historical fiction, or even things like alternative fiction.)
Ignoring the "science" in Science Fiction there
A common sf theme is "here is this change to the laws of physics, what would our universe then look like". Eg Arrival (and the story it's based on), tons of books by Egan, any book with FTL.