No reason to speculate. I certainly do that sort of thing: I read a bit of news, wonder about some of the details, look them up (on wikipedia or anywhere) and then post an in-depth article I find on the subject to HN. Usually I do that after someone's posted the main news article on HN, but sometimes I manage to ninja the ninjas. Some times the in-depth article is more interesting, or more HN-interesting, than the related news article so the news don't get posted on HN at all.

Anyway if I do that, there must be others who do so too, and probably not just a few.