Most airlines operate a seasonal schedule and add/reduce flights according to demand throughout the year. SQ for example regularly fluctuates between 3 and 4 flights a day SINLHR depending upon demand - as do others eg CZ or KE adding supplementary flights to Oz during peak times, and reducing throughout the remainder of the year.
I agree it doesn't make sense adding JQ ILO QF in this case -- as the leisure travellers that fill the back of the bus probably just won't be travelling full stop during that period.. Then again, maybe JQ would lose less money than a QF flight at the same period, who knows.
Reduced flying is never good for the employees - but I think it is great QF seems to finally be taking some risks and working out where they can save money and grow revenue in a dynamic market -- supp flights to SCL/DFW over the holidays are one example.