Why are "approving a pending duplicate vote" and "casting a close-as-duplicate vote" different actions when done by the asker?

Question

When a question is flagged/close-voted as duplicate by other users, the question asker has the possibility to unilaterally approve this vote and have the question closed. If this happens, the last close-vote is attributed to the Community user, instead of the asker.

This has occasionally led to confusion, and there is an old feature request, to list the asker as the last close-voter. I agree with that feature request, because it would definitely give more accurate information.

The only answer to the feature request says that "unilaterally approving a duplicate vote" and "casting a close vote" are different actions. This is true, as the asker has the option to just cast a non-binding close vote.

My question is, why do we have these two different actions? If the asker agrees with the proposed duplicate, why would they want to cast a non-binding vote instead of a binding vote?

Answer 1

It's all about privileges and reputation.

Any user, even with 1 reputation and without a single privilege, can click the "I agree, close the question" button and have it closed instantly as a duplicate.

The ability to cast (non binding) close votes on your own questions comes as part of the "View close votes" privilege, usually given at 250 reputation. That's a lot more than 1 rep.

Worth to mention that similar thing happens with flagging vs. casting close votes: at 15 rep one can flag a question as off topic, and at 3k rep, a user can cast actual close vote, but can also still flag. In such a case, the flag is turned automatically into a close vote, so logically, it can be applied to this case: if a user with 250 rep try to cast a non binding close vote as a duplicate on their own question, and there's a pending close vote/flag already, make it as if the OP clicked the "It solved my problem" button.