Look, I think assigning a mentor isn't a bad thing to start. It gets people who are interested or required to "mentor" (defined here as supporting the development of less tenured/senior employees) connected more easily with the target folks who need/want/are required to have mentors.

Then, if it sticks, it sticks. If it doesn't stick, it at least provides some context for both the mentor and mentee if that relationship or the idea of mentorship wasn't executed well.

Agreed that many times, it is an onboarding helper and someone who just acts as a friend you can ping in the early months of starting.