Lately, I've been responsible for mentoring other PM's. Sure there's the widely shared roadmap, but also -- I can't tell you how many documents and sheets are created that are literally never seen again by anyone other than me, and I get the feeling were created to demonstrate that they are working. It's a habit I try to break.
The reason I advocate for technical product management so strongly is I've (over)simplified the problem in my head to be that some PM's are stuck at that high level of abstraction because they're unable to communicate with their teams on the detailed technical matters on a daily basis. So they end up in a weird grey area of project/product management.