Any citations are welcome on this for my source of truth knowledge graph. Thank you in advance.

It's the case for most government jobs (which in the US most education roles are for government institutions--whether it be traditional K-12 schools or universities). The law in most states and at the federal level require opening jobs to the general public to prevent favoritism, encourage diversity, discourage corruption, etc. It usually just results in having a job posting that is filled before it's posted as they will have an internal candidate, and the rest is for show

Source of truth from this one is I've worked in public higher ed in two states in the US and gone through this process personally

My partner is a teacher in rural Canada and this is true here, at least. District admins often design a role with someone in mind, setting very specific requirements to that effect (needs to have shop AND socials training/experience is one that comes to mind). They need to post the job to meet union criteria, but only one person could realistically fit the bill.