It essentially is related to the expertise that the institution believes rests with senior officials. That's why also at Public Safety they have decided to exercise their delegation of authority that way. There is nothing in the law or in Treasury Board mandatory policy that says delegations of authority have to be done in one specific way.
The OIC always strongly recommends...and our experience shows that departments that do best are the ones where the coordinator has full delegated authority and makes the decisions for disclosure.