This is sort of a meta-question, which was prompted when I saw the another submission of the same url that I submitted reach the front page of HN. Is the HN submission tool broken?
My example:
https://news.ycombinator.com/item?id=21918556
https://news.ycombinator.com/item?id=21913030
Example of similar posts:
https://news.ycombinator.com/item?id=21918610
https://news.ycombinator.com/item?id=21916651
I'm sure there are other examples out there.
The example you list seems new indeed. Usually there's at least a difference in URL. Or the older story is a day old (stories that didn't gain traction get another chance).
This is something for [email protected] to check on.