The normal SE policy is that duplicates are only for questions. You can have the same answer on multiple questions in a technical sense with the questions being completely unrelated.
But since M&TV is not a technical sight, the mods have come up with their own scheme. Which makes no sense. Basing duplicates on answers leads to the second question, asked in a significantly different way, being closed. Then eventually deleted. Both closed and deleted question status means it does not get indexed by SE search or Google, which means searches for those terms do not come up with a result, which leads to people asking for the same movie, again in different ways. So basing duplicates on answers mean more duplicates will occur.
Also, you cannot close a question as a dupe of a question without an accepted answer in the first place.