I was booked MEL-SYD-HKG, talked to a Borderforce officer when at the airport a few days prior (due to an abortive attempt to get to HK via Auckland) and he called the higher-ups to confirm that I could leave. The data he came back with had to do with how long, and how many times I had been in Oz since 2018. More of a double check regarding "ordinarily resident" in another country, so they aren't just assuming your
PR HKID is valid.
When I flew the domestic sector to SYD, the MEL check-in staff asked to see my HKID but probably only because I asked if they could check the bags straight through to HKG. They couldn't check the bags through so had to hump them around the airport to International. At SYD, the Borderforce people were friendly and helpful and it only took a few minutes to get the clearance (gave them Passport, HKID and Crew ID) and got the impression that they checked my time in Oz on their computer. The officer in charge mentioned that I qualified on 2 fronts -
PR in HK and Aircrew. The passport has a "hold" status put on it and when you check in the ground staff have to call through to get that lifted before issuing a boarding pass. Mostly painless.