You are slightly in error. If you re-read my earlier post you will see that the AIP ref 9.2.2 is from the
Singapore AIP
This was to demonstrate the same requirements re AUS v SIN. But as you say, it or similar, appears in the Australian AIP, and indeed it does in the Weather Deviations section you refer to.
However may I also refer you to:
AUS AIP GEN 3.6_ 6.6
6.6 Phraseology. Standard phraseology exists for the declaration of abnormal and emergency operations, ie PAN and MAYDAY. Pilots are reminded that timely use of these phrases will get the level of response required. The use of non-standard terminology can lead to misinterpretation of a pilot’s requirements. This does not preclude ATS requesting confirmation of a pilot’s requirements.
The SQ flight was an RPT flight, it cannot be nor ever was a SAR/HOSP/FFR/MED flight due to the very nature of it being an RPT flight. If the Flight required priority handling then the only proper thing for the crew to do was to declare the PAN.
(Of course the proof in the pudding would be if on arrival at YSSY, did they unload the sick pax into the ambulance as a priority before unloading all the other pax?) - I don't know.
As you say "the docs are your friend" - maybe you should take them out to dinner more often.