I had the same thing happen to me. I'm flying SIN/ICN on Dec 20 and I couldn't figure out why I was suddenly seeing 2/2/2 on the KE site as I was selecting my seat. Clicking the Boeing 777-300ER hyperlink on the seat assignment page takes you to the 2/3/2 configuration. But when clicking under "The seat type may differ according to the number of seats within the same fleet type" and choosing the "261 seats" and then clicking "cabin layout again" you see the correct layout.
Any idea what a good seat will be? I'm assuming the middle section since both would have aisle access.