Usually when the word “original” is used in the context of media, it means it’s a new idea/concept/story, in opposition to an “'adaptation” from another media (like a movie to a videogame, or a book to a movie). This movie is an adaptation.

I’m not criticizing your opinion, as I really like the movie too (including pacing and direction). Only the terminology.

It’s not original, though it expands on Ted Chiang’s short story “Story of Your Life”.