I've just been trying to do some "housekeeping" on TeX-SX. A user asked a question why does rotation style work on actual coordinates and not variables in tikz 3d plot?, but then they spotted a similar question and added their example to it Why such rotate in tikz doesn't work? and set a bounty on that older question. The older question now completely subsumes the later one so it seems a reasonable idea to close the newer as a duplicate of the older. However, when I tried to vote accordingly, I got the message "This question does not have an upvoted or accepted answer". I know that, but it still seems the right thing to do to close the later as a duplicate of the former.
When I went to flag the question instead (thus creating more work for our moderators), I saw that I could flag it as a duplicate. But when I tried that then I got the same message - it would appear that because I have close privileges then the "flag as duplicate" gets automatically directed to "close as duplicate".
So it's an edge case. But if I can't close as duplicate, can't I at least flag as duplicate?
We do get a reasonable number of such incidences on TeX-SX. Most often it occurs when a question is migrated from another site: the person might re-ask the question before the migration happens, and then the question is also migrated. Eventually such evident duplicates get sorted out but the quickest way to ensure that the focus is solely on one version of the question is to close one as a duplicate of the other.
Or how about +20k users can close as a duplicate of any question.
Incidentally, on the face of it this question would seem to be a duplicate of Close-Vote impossible due to "question does not have an upvoted or accepted answer", but that itself was closed as a duplicate of Duplicate target erroneously rejected although it has upvoted/accepted answers which this one most certainly is not a duplicate of.