I can understand that it makes no sense to close a real question as a duplicate of an not yet answered question.
But this also doesn't permit me to close an exact same question (with only a few formatting changes; text is the same) which has been closed as not constructive.
I think it makes more sense to show that the question was already posted by closing it as a duplicate.
I saw this question: Closing for exact duplicate - does the duplicate have to have an answer too?, but it doesn't answer the case of a not constructive question / not a real question. It only considers questions nobody is able to answer.
So I'd ask for being able to mark questions as duplicate of a closed question (which is closed because it is off topic / not constructive / not a real question / too localized) when they're nearly exact duplicates (only formatting changes, minor text changes).