Apparently it wasn’t. I don’t remember where I saw it, I think maybe a Kyle Bosman video, but Gearbox/Randy Pitchford basically said they made the movie to pull in people who hadn’t played the games.
“In terms of the Final Fantasy that I think is the ‘most complete’; I believe Final Fantasy 6 comes close, and does stand out above the other Final Fantasies, especially because it was the last Final Fantasy to use pixel art in all of its visual expression,” Sakaguchi said.