I think what the comment gets wrong is that even in the professor (PI) / grad student relationship, it's not defined as a purely managerial one. The one-on-one meetings between professor and graduate student are often about working out a new theory, even if the implementation and experimental work is left to the student. The amount of mind-share that goes on between is nontrivial, it is necessary for work that pushes the boundaries of human knowledge, and isn't at all like an executive asking for a report from an underling.