It's not a re-positioning flight. There are many redeyes from SE Asia to ICN. Koreans prefer them so they can have more vacation time (and it also helps with connections to the US morning departures).

If you have status, then that's probably why they opened them for you. Asiana and Korean Air both often offer business class seats like this with economy service, usually as an op-up for oversold flights. Lately, however, they've been introducing paid upgrade for the seat with economy service. In your case, I would just keep these seats and enjoy!