permission problem

The permission "subscribe to all content types" doesn't seem to do anything. If you check only that box, subscriptions aren't available at all. You have to give individual permissions for "subscribe to blogs," "subscribe to content," "subscribe to content types," and "subscribe to taxonomy terms" in order for subscriptions to be available. If you select all of those four but don't select "subscribe to all content types" it all works anyway. So it appears that "subscribe to all content types" doesn't really have a function. Am I correct about that?