I'm aware of the "How do I change a close vote to a duplicate?" question from a few years back, but mine's slightly different
A user asked a question, which wasn't clear. I left a comment explaining what information we needed, and left a close vote for unclear what you're asking. Some time later, the OP came back, and edited their question with the missing information. With that information in the question, it was then clear it was a duplicate. So, I retracted my unclear close vote, and went to close as a duplicate, but it wouldn't let me!
I can understand that there's a desire for stopping people changing their mind on a close vote when the question is unchanged, as covered in the older meta question. However, I can't see why I shouldn't be able to change my close vote after the OP makes significant changes via a big edit to there question
Could it be changed so that you can change your close vote (eg unclear to duplicate) after major edits to the question?