I put your submission in the second-chance pool (https://news.ycombinator.com/pool, explained at https://news.ycombinator.com/item?id=26998308), so it got a random placement on HN's front page. I picked yours rather than this one because yours was posted first. I also changed the title to the article's subtitle because it was more interesting.
Looks like another mod later put the current thread in the SCP, not realizing I had already done that. We don't keep track of everything (there's too much to keep track of) so this happens sometimes, and no doubt the different titles made it harder to catch the duplication in this case.
In any case it was a great submission and a bit of dupeiness is a small price to pay!