HN will post jobs from YC - usually they put which YC class they are from. You can see only these posts under jobs at the top: https://news.ycombinator.com/jobs
YC startup founders have access to post those job postings as part of going through YC (or being YC alums).
In the past these have always been clearly labelled as job listings. This one just had a generic headline that made it indistinguishable from user-submitted content.
Agree with that. I wish they were still clearly identified, it would make it easier for me to filter them of the feed.