This statement can be ONLY true if the agent is somehow able to "convert" a $ ticket to a reward ticket OR request a reward seat on any service flying that AND is confident to get a reward seat released.
Now if ANY part of the above statement is true, then why not allocate the necessary number of reward seats to the customer EVEN before issuing the change notification in the customer's QF app, so that the customer doesn't have to call the customer service?
So far I never had any reward flights cancelled, so I'm not sure if there has been an "enhancement".
This statement makes me think that the agent wields more power that they let us believe ... if MMB can show $ tickets as part of a change notification issued for a reward booking change, then QF has some mechanism to release more reward seats even before the customer intervenes. So why not just do it so that the customer need not worry about the change in their booking.