It must have been a recent change. Just like Myer, if your order is paid for by David Jones gift cards are not eligible for cashback.
I found out after I got a $0.00 tracking.
Be warned when you get your discounted gift cards.
Edit: Cashrewards noted the change was effective 29/06/2021, however, I've had cashback paid out since.
Weird thought all stores were like that.