Does DL plan to use the A330neo from any other destination through ICN, other than MNL and SEA during the winter season?

I could not assign seats on the MNL-ICN-SEA legs for a flight in January 2021. Further, the My Trips section of the web site is showing "aircraft change" in ICN.

I actually booked this same trip, SEA-ICN-MNL for April. Connecting time in ICN both ways is between 2-3 hours. I remember being prompted to pick seats only once each leg (system seems to want to assign you the same seat on the same flight number - no big issue with me there).

I booked this flight again for December, returning in January. The return leg now shows a 5 hour layover in ICN, and the itinerary shows "aircraft change" in ICN. I still could not pick seats on the return, even after giving it a few weeks (I figured it was still too early to assign seats, even though seat map shows some seats already taken in all three classes). I finally called the reservations phone line last night and the agent confirmed that there would be an aircraft change, and that he had to manually assign me seats on both legs (when typically, you only pick once if it were on the same equipment).

I did mock bookings for ATL-/ DTW-/ MSP-ICN flights for the same time period as my return and all are on A350s. Only SEA and MNL are on the A330neo.

I believe DL will have a total of 7(?) A330-900neo's by end-2020, assigned on SEA-ICN/ -PVD/ -NRT (and -AMS?).