SEA Premuim Economy Capacity/Flexibility Drastically Reduced
 

EVA will shortly be converting a SEA regularly scheduled 777 (with PE) route to 789 (without PE). This change drastically reduces PE availability, reduces the availability of total flight times under 21 hours, and will drive PE fares upward.

I was scheduling a trip (SEA/BKK) for September 14/October 20 the outward bound had 6 options for total flight times under 21 hours. The October 20, 2020 return flight (BR 26 now 789) had only one option for 17.20 hours total time, the next 2 and only options were over 27.0 hours total time (27.55 & 37.15 hours total time).

This sever reduction in reasonable PE Fares is going severely increase consumer competition, increase purchase lead-times for reasonable route times and drive fares up. I find this very distressing for a loyal 2 decade EVA customer.

I too am a frequent PE flyer out of SEA. While the move is negative for individuals, it certainly makes sense from a business standpoint. At this point the SEA-TPE demand is heavy with passengers on their way to SE Asia (primarily Vietnam where airfares are super low), and then the tech crowd usually traveling in paid J with corporate contracts. PE is full only by virtue of upgrades and the relatively small Taiwanese population local to SEA.

From my individual experience your assumptions are not true.

I would encourage you to do an easy experiment the next time you're booked in PE on the SEA-TPE flight. Ask the agent at check-in how full the PE cabin is. I fly this route 10-12 times a year and the answer at check in is never more than 50% booked. However, when you actually get on the flight I guarantee you will find PE > 80% full. If you pay attention to the pre-boarding announcements, you'll often hear 10-15 Gold and Diamond members being called to the podium to get their new boarding passes from Econ to PE.

Are these OpUps (Y is full), free upgrades (United CPU style), or paid/points upgrades (Mileage or $$$)?

In my experience from YYZ to TPE the PE is full too. Or almost full but rarely do they upgrade to business as there is one or two seat empty. Sometimes they do upgrade when full. The upgrade comes from EC being full. Business doesn't seem to be full.
PE for BR is one of their flag projects so I am surprised they are planning to remove it.

Definitely operational + status related. I know a couple of BR reservation agents and they are actively encouraged to overbook in Y on this route, knowing that PE will have room to absorb op ups.

That's exactly why I jumped from Cathay Pacific 20 years ago. I got tired of flying Slave Ship Class for 14 hours.

The PE cabin is fairly small too so I am surprised that agents are encouraged. In the sector that I fly I don't see them upgrading too many into PE as it's fairly full.
I certainly will change from BR if they do away with PE from YYZ.
But not too many airlines have a good PE unlike BR. Honestly for the price they charge they should market the PE lot more. Many would pay for the extra for the comfort. As any OP mentioned a lot of Asians still use travel agent and in my experience they don't give too many options and many may not even know about the PE.