There’s a reference to it in the CX forum (unfortunately the historical data is no longer available to view on Flightradar24):
https://www.flyertalk.com/forum/34097509-post26.html
But it prompted my memory that I also saw this a few times on FlightAware a few months ago, thinking to myself, wow that must suck for passengers in Y!
The 90-minute stops in Seoul to/from Shanghai (that UA and a few other airlines do) kind of suck too, but I've endured mine by convincing myself that we were still flying. Anyway, you guys are right, unlike CX, UA doesn't really need to fly NYC-HKG nonstop because it can and does sell tickets on flights between NYC and California. I guess I don't really see ORD-HKG happening soon for the same reason (Russian airspace is quite useful on Westbound flights, especially during the winter months). But, I do predict UA will try to do more than one flight to HK. If so, I'm guessing SFO would get a second flight? Or maybe give it to LAX instead (this might shut out AA)?