Inception is literally about dreaming. I don’t know what criteria they use to lump it in with science fiction.
The use of fictional technology to induce the dream state would qualify. And within the "rules" of the world in the movie, the characters' navigation of those layers of dreams is explicable by science (as opposed to, say, magic).
But yeah. I consider Inception to be SF, but just barely. It's more of a heist movie with some SF themes and a healthy dose of mindbending.