me too.
I fly to China and back to iad/dca once a month. Never saw such a thing. I always have to use a SWU to do u/g.
I was highly doubt too, but there were so many 1,2P got upgrade and reported on another online comminuty. I am not saying this would happen every time, but PEK-IAD, PEK-SFO routes definitly gave more free upgrades than any other routes.