Erin Pace. I definitely understand your line of reasoning. I also agree that the findings, in part, would depend on existing organizational culture. For instance, perhaps in a work environment where everyone wants/needs to know everything, Ccing the boss may not necessarily be a bad idea.
I think, the most important take away here is that, there are some emails that superiors do not really have to be Cc’ed. For example, when passing an information (through email) that does not directly concern the leader to colleagues (having the leader in Cc) may send mixed signals, one which signals low psychological safety and fear.