On Engineering Leadership: Focus on the what, not the how

It’s been my experience over the past 30 years that engineering managers focus on the engineering, i.e. tools, resources, training, skill sets, recruiting, etc. In other words, the “how.” Project and product managers focus on the “what,” i.e. the requirements, the results, the schedule, the budget, etc. Why are these titles and responsibilities often confused? I see this often in HN posts. Does anyone else see this confusion?