I just got my five-year anniversary upgrade. Flew to JFK via YVR in J five days ago and at check-in the assistant picked up the phone as soon as she typed in my name. She was speaking Cantonese, which I cannot understand, but I got some of the gist there were no F seats. For the return leg, checked in at JFK and again I could tell something had come up as the guy was looking around for a supervisor after typing in my name but could not find one and gave me my J boarding pass. In the lounge just after boarding had started, I got a message to see a CX rep and there it was my first class boarding pass all the way to Hong Kong!
As others had noted the letter V was on the boarding pass. Also I was able to print my boarding pass on both occasions so that is not always a telling sign. IMO First is much harder to snag than J. I think CX has a strict policy of holding onto F seats until the last second so there was no way for them to give it to me at check-in. I imagine Y or Y+ to J is much easier as more seat availability.
Cannot comment if I had got upgrade on outbound then I would / would not have gotten it on inbound but hey it was an amazing experience that everyone should get once in their lifetime. The hours just flew by. No recognition on board that it was my five-year anniversary but ISMs on both flights were not the best. However, First crew were immense!