I would interpret it in a different manner. August 13th is a Sunday, and that is the busiest day for business travellers from Australia to the USA. As such, QF is withholding the D seats at this time and hoping to sell more full priced J seats. Hence its showing J9 D0.

Note there are still 11 unallocated J seats showing in the seat map for that flight.

But its much harder to come to a conclusion about the economy cabin since there are so many more seats covered by those fare buckets. The best indicator is the availability of the heavily discounted fares such as N, O, Q and the award seats X and T. None of these are available for the outbound flight, so there may be as few as 9 seats left in economy.

The return flight is showing N5 Q5 so still some of the cheap seats available, but no X or T award seats. But just based on it being a Sunday flight I would expect its going to fill up with last minute business travellers (in most classes).