What's your point, that people should not read content that's over a month old?
This was a great article - I read it when it came out - three years ago. Unless there's an update, it's worth noting that this is a three-year-old post.
This happens often. It's generally a good thing.
See also: https://xkcd.com/1053/
In this case, this is essentially a repost of something PG put up three years ago: https://news.ycombinator.com/item?id=1071429
It's simply not detected because it's in a different publication on a different URL. If the dupe system was more "effective" it wouldn't even show up, as it's exactly the kind of repost that is intended to catch.