Originally Posted by
NYC_Girl
That's exactly what I'd expect: The value of GPU is fixed, so if UA can use it to serve a cheap or an expensive product, it'll choose the cheap.
All I can say is that UA's published upgrade guidelines do not take this into account. I don't think we have enough information to be able to state definitively that UA isn't doing something deceptive behind the scenes, but I would be surprised if they had the technical acumen to pull this off even if they wanted to.
The published order is to upgrade passengers from P+->J first (meaning, people with P+ tickets, not Y tickets that have already been upgraded), then to upgrade Y->J, and then to upgrade Y->P+.
I can promise you that they will not send a J seat out empty if you have a waitlisted instrument for it, just because they can already mark the GPU used by seating you in P+. (Or, at least, it would be against policy and would likely get you a nice customer service gesture as an apology).