Just adding a data point, flew CI74 AMS-TPE last week, paid 299E for gate-upgrade from Y (fare code N, discounted eco) to PE, seamless process, just ask and swipe of a credit card you have a new boarding pass in hand.
But the PE on A350 is not worth it, the seat might recline more and be wider, but not angled at butt level, so you will keep sliding down when reclined. Hard to sleep in.


Will try to see if I can score business upgrade on way back tomorrow, if it's bellow 799 I'm in, the ticket was cheap enough