Why is this labelled sci-fi?

Who cares how the term science fiction is used? There are hundreds of millions of English speakers and how the language is used and abused is fluid. You're going to have to be the one who deals with it. To help you, I'll suggest adding the word future or some synonym or derivative. I'm not arguing about the definition; you might have been right at one point but what's right changes when the ignorant gain a numerical advantage.

You would be right if science fiction was defined as technology that either does not exist or was not yet invented, but googling the definition I found that it is either technology or science. So, an alien species of spider-rocks would actually be science that was not discovered yet, and it is the main point of the plot, so it pretty much fits the bill of science fiction.

Because science features prominently in it, and the story is made up from elements that are real, but which did not happen exactly as presented. The alien element that is presented is entirely conceivable as being possible, given what we known about bizarre animals here on Earth. That's science fiction.

But I would agree with you that sci-fi is hardly a legit genre, on its own. Drama, action, comedy, suspense, horror? Sure. But sci-fi is usually just one of those, set in space.

That is, unless it relies on completely made-up technology and outlandish imagery to entertain as much as it actually tells any story. In that case, it goes beyond fiction into fantasy territory.

Your definition of sci-fi is incorrect. That is all.

Movie has science and has fiction, end of story.

Wat? I thought this actually happened. O.O

because it isn't a ROM-COM. Has science, IS fiction. Not sure why peeps have to over complicate the definition of sci-fi these days. pretty simple to understand as is

Gravity is very Scifi. Even by your own definition.