I expect Australia will do what they are already doing, getting airlines to do the verification at checkin. Last time I returned I had a Somali test certificate that failed some of the detail in the exacting requirements of health.gov.au. The checkin clerk got as far as "test certificate" and my name and I was never asked for it in Australia
Data point for you, Azerbaijan claims in TIMATIC to require a "digital certificate with QR code", and in fact the signs over the immigration counters specifically mentioned this. I handed over my epic fail Australian certificate and the customs person didn't even blink.
A commendable application of common sense in both cases.
BTW I have heard of others having endless problems with cafes, restaurants etc in some countries because of lack of QR code. But so far my green google pay certificate has worked fine. So it seems to vary.
Cheers skip