I just wanted to follow up here. CX ended up sending me a letter with a one-way, one-segment, one-class space available upgrade valid for one year. The letter set out that, per CX's review, there was no actual danger at any time. Sounds like this was, at the end of the day, a minor thing.

What's coincidental is that I had already decided to give CX another try, and had just bought a cash RT SFO-China ticket on them in F anyway. So I will have to save my upgrade for later!