People can grow into their roles. You don’t expect junior devs to know everything one day one, so why would you expect a “junior[1]” manager?
[1] I know the article is about senior managers, but it reads as though the mean “somebody more senior than me” and not “somebody who has been managing a long time”
Genuine question: how do we train managers, then? Surgeons have pigs, but even then it's not perfect, and there comes a point where they have to perform surgeries on actual humans (hopefully under supervision).
Maybe they aren’t good at it, or maybe they’re new to managing and this is one skill where they will get better.