I have, but these were generally founder types that accidentally became managers. They weren't "career managers." The career managers delegate that work.
all the time? not on technical issues, unless it's a TLM or the IC is entry level and it's pretty basic stuff they need help with, but absolutely on navigating organization, communicating, prioritization, and so on...
Has anyone ever seen a manager mentoring ICs? I haven't. This is a senior/staff/principal responsibility.