I've gotten a lot of pushback (from two different companies) when I suggested openly that any PM should have an extensive if not intimate understanding of the projects they're managing. They should realistically be able to do the work they're delegating, because you routinely need that level of understanding if the ones you're managing expect to get useful information out of you. If the manager doesn't understand the project, it becomes a repetitive effort of "let me ask the client, I'll get back to you" and you end up wasting tremendous amounts of time.
I get the spirit of what you’re saying, but to realistically be able to do the work seems a bit far. This would be hard to apply to even Steve Jobs. Maybe another way to phrase it might be that they should intimately understand what the vision of the work entails rather than need to always ask for the next horizon.
The entire spirit of the article and research though is that workers make better managers than pure managers. They don't need to actually DO the work, but understanding to that level is invaluable and why Steve emphasized it so much.
