They being QF can always do an equipment swap.
Got this with them long time ago, SYD - MEL, wanted a 330, booked a 330, walked (after an overnight stay at the Ibis Budget Sydney Airport) to T3, had, with so much positive attitude, and hope, got to those gates facing the QF maintenance area, at SYD T3, and to my horror, yep, there, waiting for me, at the gate I was hoping to go on the 330, guess what was waiting for me, yep a 737.
Until you get your bum on the 330 seat, and the 330 reverses off with the tug, and taxis off for the taxi way, then runway, and takes off, then you know you have made it.
If you are lucky, you get to meet your 330 down at the end of gates 10/11/12 at SYD T3, and then you will feel the double gate entry to plane experience.
Very very rare for QF to bring their 330 into Adelaide these days, so I do look forward to my next QFi flight, will probably be east coast Aust to Japan.
Their (QF's) flights, to NZ they probably might swap to 737 if they wanted to.