Suppose you have the next setup for usergroups:
-Group1 --> Group 1 category
--Group1 manager --> Group 1 category
Suppose you would want only the managers to be able to setup an event. How would you setup this. In my setup I would only allow managers to add events.
The standard setup is inheritance for Registered, Group1 and Group2 and allow for manager. The other way around would mean that registered users have access to setup an event.