[walrus1066]

"The ways engineers are terrible managers non-technical managers are often terrible too. In addition to that, they also know less about work itself and are more likely to be insecure about that."

I would put that as another human/personal trait, the ability to openly acknowledge ones limitations and delegate/defer when someone else has more expertise than you. For example, when making a technical decision, deferring to the tech lead & individual contributors.

If anything, a technical manager whose tech skills are/have slipped away is more likely to be insecure than someone non technical.

[watwut]

Technical manager needs to defer decisions too. No amount of knowledge makes it good idea to micromanage or not to build consensus with those he manages.

However, he still have better ability in deciding who to defer/trust to, better sense on bullshit vs reality, better idea about nuances of decisions and knows words people use. That shows up in how meetings are moderated, people know it and also some will always try to game the manager. Non technical manager is reduced to parroting sentences and attitudes he does not understand fully. Knowing something is not a disadvantage, ever. Not knowing something is.

Every manager needs to make some decisions too. And in there, knowledge helps. Knowledge that slipped away is better then no knowledge and worst then relevant knowledge.