Assume you’re referencing the YC HN hiring ADs.

I don’t even see Principal Engineer listed as an open position on the link they provided in the AD or on YC’s job section:

https://jobs.lever.co/buildzoom

https://www.ycombinator.com/companies/buildzoom/jobs/

Here’s screenshot of the HN AD as a point of reference, since it will disappear at some point:

https://ibb.co/SQSG3mw