This particular circumstance can't have been contemplated by the 12-month limitation in the terms and conditions. As it couldn't have been comtempated, the condition shouldn't apply.
The 12 months is designed to fix problems like missing flights, wrong class of travel, credit for comfort seats, or original routing credit. All sorts of things where the passenger has the opportunity to look at their statement and say 'hey, that's not right'.
In this case QF would have argued there was no error... it determined the number of miles between KUL and BKK and credited the points and status credits accordingly. Now they have recalculated those, so they also need to recalculate the points awarded.