For the page restrictions dialog, when there are restrictions, by default the page author is added automatically to the restrictions list and it shows the "Has no access" and "Can view and edit" hints. This makes it clear to the user what behaviour to expect.
However for TC, the restriction dialog is hard to understand. Some users expect the list to be a block/disallow list and it's harder to figure out how to restrict everyone else.
Ideally the TC restrictions dialog should behave consistently with the page restrictions dialog.