Perhaps I am not explaining the situation correctly.
(Another) system failure has occurred at Airservices Australia ATC to which the ATC response has been to reduce the amount of aircraft being handled so as to restore an appropriate level of safety.
Consider the situation that would exist with the ATC system operating normally in the morning peak period. Then "this" (whatever) failure happens.
If it is then necessary to reduce the amount of traffic in the air to restore a safe operation then by definition, in the time between failure and the actual traffic reduction, taking effect, there was more traffic in the air than could be managed with the requisite level of safety.
If that statement was not true, then why reduce traffic?