I found this question here on Meta from 2009, and it was closed recently as a duplicate of a question that was posted much later!
Why is that? It's not just that older questions can't be duplicates of newer questions, but I also wonder why people dug up this old one and started to cast close votes on it all of a sudden; it hadn't had any activity for years.
Not that I have much reason to have it reopened or to have the newer one closed, but I'm just curious.
Given the responses, this question might be better off as a feature request. So here goes:
Change the text in the "Closed" notification from "This question covers exactly the same content as earlier questions on this topic" to "other questions".