True, but we don't count posts as dupes unless the story has had significant attention in the last year or so (see https://news.ycombinator.com/newsfaq.html), and arguably there hasn't been significant attention since https://news.ycombinator.com/item?id=7530427.

That shows just how great the concept is.

what other built-in ways are there to query stories posted to HN?

There aren't any, that one is new. You can play with the Firebase or Algolia systems though.