JomVanFliet: Should be easily circumventable by going through a VPN and temporarily "relocate" to somewhere else other than Down Under, no?
Dont think so, as the bank's account country will be the limiting factor, as a bank would lose out on international fees.
So your you VPN may say one thing, but if you are paying international fees (as the store will definitely not pay for you), it will be "easy" to infer where you are - and the bank sometimes also does not allow the transaction as it can suspect fraud.
That may have been true a few decades back, but now banks are more alert when you "change" country (hence tales of people's card being block when abroad for example) not because of security ofc, but because is a good opp for the bank to charge fees!
This will be interesting to see how it plays out, as here generating/having virtual CC is a thing - its what i use here, each purchase a different card - so its not really something that bother or useless for the purpose of age checking (having CC to my knowledge is common when one here is very in deep in debt, as beyond that there is no purpose/advantage over debit card = the latter being what most use).
Interesting times, need to get popcorn.