I didn't expect a dev to chime in. Especially this soon! <3
Sorry, I know it's unrelated to the OP, but thank you for the attention you provide, even if it's small. Most companies just make a "suggestion" forum and then they just ignore it pretty much.
Anyway. OK, I can see that I suppose for Usergroups, but what about nodes? Actually, do they inherit permissions of the category they're under? If so, I guess XF's point is pretty solid.