In my personal opinion, your question is not off topic. Sure, the movies are fictional, but your question was (implicitly) about the real portrayal or usage of an actual art in that medium - and it even produced an interesting answer pointing out a usage well before most of us would remember.
Speaking as the ♦ mod who actioned your flag, my observations are:
- the responsibility of a ♦ mod is to act as an exception handler, dealing with things outside of the processes and handlers already built into the site. I declined your flag because it didn't need moderator attention.
- whenever practical it has to be a community decision to close a question. The only time I will vote to close a question is when it blatantly needs it - if there is any doubt then my job is to stay out of it and let the community decide. Moderator votes are instantly binding and at no stage should a single moderator dictate the direction of the site by closing questions or deleting things they personally don't like.
- if you are so sure it is off topic you can just delete the question yourself. There are ramifications to that because there are already votes and an accepted answer, but those are ramifications you should own if you do it - you shouldn't avoid those ramifications by raising a mod flag and getting a mod to do it.
- maybe you are totally over analyzing it. Like I mentioned above there is a way of viewing your question where it can be totally on topic. Maybe your view is too narrow and/or fixated and your question is fine in the view of the majority of the community?