query_posts() as the example: if the correct/accepted answer uses a different function - more accurately, uses a more correct implementation technique, then I say yes: re-tag the question. But more importantly, you should also edit the question to reflect a more-general question.
To generalize the example, I see this as a case where a user asks, "how do I use this not-best-case (or worse, wrong) implementation method to do X?", and the community responds with an explanation regarding why the OP's implementation method is wrong, along with a solution using the correct/best-practice method. In such cases, it is useful to generalize the question, and re-tag.
I don't know how far that answer extends to other use cases/scenarios, though.