The fact is that the requester is always at a knowledge disadvantage, because you don't know and you can't know what is actually there. The government has to provide you with what sections they're relying on, so the blank page would have, for example, “section 21”, written on it for your information, so that you would know that's the section they're relying on to give you nothing.
This is where the order-making power becomes valuable, because at that point, you are able to go to the commissioner and get an enforceable order. The commissioner or his delegate gets to look at those documents and decide whether the government has properly applied, in a limited and restricted way, the exemptions that are in the act.