Plus when you click on the link, you get a mission statement and description of the service before the job description, which is not totally unusual, but still makes it possible to bait potential clients rather than applicant prospects.
The glaring inappropriateness of those posts is also a testament to how good the moderation is on HN. Very few posts on the front page feel like ads at all, except for those ones…
IMO, these definitely fall in the growth hack dirty tricks bin…
From the FAQ under Can I post a job ad:
Another kind of job ad is reserved for YC-funded startups. These appear on the front page, but are not stories: they have no vote arrows, points, or comments. They begin part-way down and fall steadily. Only one is on the front page at a time. The rest are listed at jobs.