Thanks all.
The Star Alliance website was useful here, thanks for the link
Thai-Kiwi . It show MEL to have Gold track (express path) for outbound AirNZ, which is what I experienced. No mention of inbound, which is also what I experienced. Similar for SYD departures (priority path) - but this doesn't match what
Murihiku experienced. I will check next time I am in SYD.