I think they took the right ones. United doesn't want to buy the ones that are about to expire. They want them to expire. There was a discussion in the PP thread about having to make a gamble about having to trade PPs so far in advance of expiration - and that's exactly what you errantly have done with the PPs expiring in 2027. Maybe you'll get lucky and get a sympathetic agent.

If I understand the rules correctly, you had until end of March 2025 to sell the points expiring this year. The time to exchange those are 8 months past. The ones they are taking now, and the ones UA has apparently relieved you of, expire in 2027. At this time of year, It's not a first in / first out situation.

From UA:
"And, you have the ability to exchange your PlusPoints for various perks through March 31 of the year prior to the PlusPoints expiration date".