I think the assumption here is that at least the tech lead and senior developers, and possibly delivery lead, report to the EM, so the EM can speak for them (hopefully after consulting them, of course). QA sometimes also reports to engineering, or may not even exist at all. Designers are, unfortunately, often overlooked when making schedules...

But I think the simplification comes from the idea that the EM owns those decisions, even if the EM doesn't make them in isolation.