I recently asked a question about when Beauty and the Beast was set, it has since been moved to the Movie and TV SE site, here.
Are questions of this sort not fit for this SE site?
I don't think the problem is to determine if it's on or off topic, because it's on topic.
I think it was migrated because the question was better suited to movies.stackexchange. i.e. The question will be more likely be to answered (or found interesting to answer) by a movies expert than by a Sci-fi expert.
Migrating question is not a trivial decision, it's highly suggestive. There is a huge, blurry overlap between Sci-Fi StackExchange and the movies & literature StackExchange. As an example, I was surprised when this question was migrated. But It's true that it may fit better on movies.stackexchange.
Therefore, I urge Mods to be more cautious when migrating question. As the last word, I will quote this recent blog post.
But focus on the questions that aren’t on-topic, or aren’t getting answered – snatching someone’s question (or answer) away without any forewarning is a slap in their face.