Delta.com shows KE seatmap with available seats. Even if you try to book the date really far from now, you'll see that only middle and rear parts are left. Based on my experience, KE usually does not open front part to anyone even to TA or KE office. Not sure how they treat to million milers. Those seats are opened only at the flight date, so all of my pre-selections were changed to somewhere else (better seats) at check-in. KE is doing this because many valuable passengers (elite-status, or non-elite but VIPs) do not care where to seat until check-in, because they're usually old and internet seat-selection is not a general stuff in Korea yet, so they should leave many good seats. Also many passengers are not arranged seats before check-in, so it is hard to guess load factor based on the number of available seats.

If you can see better seats through delta.com, call your TA again and let them grab for you. If TA sees different seat availability from delta.com, I don't know what's going on there.

By the way, 4 seats in seatcounter.com is the maximum number for KE.