Qantas will refund but you are gunna need to push hard, they are just not drawing attention to their policy:
Compensation and Refunds Policy | Qantas
Customers are entitled to a refund in the following situations:
If we cancel your flight and we cannot offer you suitable alternative arrangements.
If we delay your flight to the extent that you have to cancel your travel.
If we make a significant change# to the scheduled flight time and we are unable to book you on an alternative flight that is acceptable to you.
If we cause you to miss a connecting Qantas flight on which you have a confirmed reservation.
If we are unable to carry you and you have a confirmed reservation.
Of course any conversion to a credit will likely create additional barriers.
However, if I booked a flight to travel on a certain date and the airline cancels it and offers no reasonable alternative, consumer law would indicate I am entitled to a full refund, not a travel credit. If they obfuscate I'm sure the ACCC may have something to say about that.