This matches my experience. As a staff engineer I also did a lot of PO work and the fact that I was also an engineer on the team helped me ask customers the right questions. As an EM, I coordinate our Product processes but engineers on the team play a huge role and decisions are always collaborative. On teams I've been on with a dedicated PO/PM, the PO just ends up trying to micromanage the engineering team and pull people into a lot of useless meetings. Don't get me wrong, there are good PO/PM folks out there, but the vast majority I've worked with don't fall into the "good" category.