If you are born in Australia to parents who are residents and citizens of Australia and have never actively sought citizenship of the country of your parents or grandparents birth, and in some cases, have never even set foot within that country, then I fail to see how that country can claim you as their citizen without you having any say in the matter.
But when the shoe is on the other foot… let’s say you were born in Korea, because your dad was the rep for Foster’s brewing and was doing a two year stint there… under your rules you would be Korean not Australian. You have no say in it.
The logic is not whether a country can claim you or not, it is simply a matter of fitting in certain boxes.
I have a daughter and son-in-law who took British citizenship a few years ago, and fair enough they were working in good jobs for many years (became citizens after seven years). That’s morally the right thing to do I think, if you are benefitting from a country, paying taxes, entitled to a pension… you should be able to vote!
Since their return to Aus, they have had two sons, neither of whom have had their births registered as “British Citizens” yet both undeniably are.
The world is not the place it was a hundred years ago, and perhaps it’s time to forget the parochial notion of “nationality” - much in the vein of French President Macron’s response to Trump’s “make America great again” - which was “Let’s make the PLANET great again” we live in the world now, not just some piddling little island on it and on your return your parents would have to apply for a visa for you.
Friends have comparatively recently adopted a child from Vanuatu - that process took them almost three years. Would your parents be happy to stretch their two year stint to five just to get their new Korean baby a visa? Would that even be fair?