I was just op-upped on CX466 HKG-TPE (Y to J). The J cabin was pretty full and I'm relatively sure that a big chunk of the pax were op-ups because of the holidays. When the meals were served, I saw a number of Y class meals being distributed, as in the full Y set-up (plastic containers instead of china, etc.).

It's possible that some of the op-upped pax had special meal requests that weren't available on short notice for J meals. The Y meal served closest to me had a pink foil lid with a sticker on it (couldn't make out what it said though).

I hope it wasn't because there just weren't enough J meals to go around and they served op-upped passengers Y meals. I personally did not partake having gorged myself in the Wing before the flight.