I am from regional Vic and flew out of SYD at the time. A private PCR test was required. This was very much NZ's decision to make, and would have had no input from the AU or state govt's. A private test generates a detailed result, which the mass vaccination clinics do not.
NZ did not specify who to go to, but they did mandate the details required. A text message from the mass vaccination clinics did not meet that.
Information for air and sea travellers about entering and leaving New Zealand.
covid19.govt.nz
I went to ClinLabs in Traralgon (Vic). It cost $150 and I got the result 21 hours later. Any of the major pathology labs do them, but only from certain testing locations.