There appears to be a difference between Australian and US and possibly ICAO procedures which triggered this event.
Without getting too technical, there are different levels of fuel urgency. In the US and most other parts of the Northern hemisphere there is a level of urgency best described as "If you screw us around a lot more you WILL have a fuel emergency on your hands" This is NOT an emergency, nor does it REQUIRE any expedited handling. It's a courtesy call that the controllers can try and smooth you in, or there's paperwork for them. Apparently the Aussies don't see it that way. Stand in line and wait your turn or you ARE an emergency. The UAL flight never declared an emergency, they demanded a certain runway instead of the inevitable delay to go to the one the Aussies wanted them on. It appears the Aussies forced the mayday on them.
Mind you, most international flights arriving Sydney have been airborne a LONG time, there's a LOT of them and fuel plans are, well, fuel plans. Winds are winds and don't always obey the forecasts. As mariners you can appreciate that. Fuel getting close and terminal delays requiring diverts to alternates is not an unusual occurrence and I suspect they get "requests" a lot, some carriers being more nervous than others. But it's a VERY busy airport so they don't need this disruption all the time.
I suspect this is a hard ball game.
(Disclaimer, although I am in the business, this part of the world is not my turf).