Qantas does specifically tell passengers this, in the screen shot previously posted you will see that:
Note that this is displayed for all online bookings regardless of which QF portal you are using (in the above case it was from an award inquiry window in my FF area), its displayed before any fares and the user is given the option to not proceed.
Qantas are entitled to put in place their own policies (the excuse given for them is probably a red herring and something of an irrelevant sideshow), the customer is given the option to agree and proceed or to not have any further participation in this offer to treat, I don't see anything unreasonable in the situation at all, if you don't like it then go elsewhere is all that is left to say, which is exactly what the OP as reported they did.