EC is fully refundable at any time. So just call in a cancel the EC seats if they don't want to pay the $$$ and get a full refund now.

And on Asia flights it actually isn't too uncommon to have tour groups or travel agents put holds on big numbers of seats and assign them but not ticket them. This could have been the case here. On a recent TPAC flight I remember the seat map being full 2-3 months before the flight and then opening up and being quite empty both up front and in back closer to departure. Sometimes it may also have to do with a potential equipment downgrade (747 to 777 or similar) so they block of many of the seats in back