http://www.paulgraham.com/makersschedule.html
To your second point: Ultimately, the PM and the people they work with (engineering, design, PMM, research, etc.), are a cross-functional team. The PM shouldn't just provide a list of what to build; the PM should help lead them towards figuring out what to build, collaboratively, together.
PG doesn't assign PM to manager's schedule. You can see engineers themselves running in buckets of maker's and manager's schedules.
Mindset of PMs being "managers", who must "lead" and unblock engineers & designers is deeply flawed and creates silos, turfs and dysfunction. Reality is that the notion of product is continuum between engineering and product management functions. One hardly need to manage other. One definitively need to partner with other.
Maybe it was hinted at in the article, but while someone's job title may be Product Manager, they'll most likely be working with engineers who know far more about the product - it's capabilities and limitations - far more than the PM. Don't take it personally if something gets shot down, or if something you didn't know about is inserted into the monthly plan.