The most common scenario would be two poorly-asked questions by the same author. Yes, these could be closed individually as NARQ - but closing the second as a duplicate of the first emphasizes the need to fix the question rather than just reposting it.
Another (albeit somewhat less common) scenario involves a question that's simply too broad - "how do I learn to program" and its ilk. Again, they could be individually closed as NARQ, but in this case dup-closing can reduce the need to explain why asking for all of the world's knowledge in one question is a bad idea EVERY. SINGLE. TIME...
The final scenario - which I think you've hit on here - involves a question that... Probably is a real question. Maybe it was originally so poorly-written that some folks didn't realize this, but the fact is it's on-topic, specific, and the answers reflect this - so closing other questions as duplicates is appropriate, so long as the original (or some original) gets re-opened. These scenarios occasionally warrant dup-closing in the opposite direction (when the more recent question is better-written) and merging.