Managerial mentorships are defined by the working relationship.
They are often implicitly enacted by the nature of reciprocation between roles: the manager needs specific outcomes and the individual contributor needs more context, so mentorship on project-level quality—the “right” way to do things—comes naturally; management roles also entail career guidance which also comes from a heightened vantage point, either through experience or at least on understanding of organization process and expectation.
Contrast with technical mentorship: they’re easily presumed to entail one another, but the latter may benefit from explicit definition.