My theory (and it's only that, a theory) was that SQ were being highly opportunistic with that attempt since the Free Trade Agreement between Australia and the US was about to be signed at the time, meaning that the air rights for transpac flights ex AU was about to be essentially carved up between DL, VA, QF and UA. I say opportunistic because it makes little sense from a routing perspective for SQ to route their north america flights so far south in the first place. Their existing SIN-ICN-SFO and SIN-NRT-LAX flights make far more sense. I suspect the Australian government called them out on it, and you don't hear a peep out of SQ about it.

West coast of the US is the extremity of EK's network (LAX-DXB is one of the longest routes in the world); flying transpac from Australia does not help cut that time down. So I'm struggling to see how flying transpac fits into their strategy/business model. Unless they want to spend a lot of $$$ to turn an Australian East Coast airport into a mini-hub for flights to South America or something, then flying transpac could make sense to boost hub traffic as it fits in with that strategy.

That said, it's a pretty profitable route (paying $1600 in low season to fly home says a lot), so I can't blame them for trying/floating it out there. But I wouldn't be surprised if the Australian government slaps them down like they did with SQ on the same grounds.