[Treeve]

The correct answer is: they were never correctly imported if the date of manufacture isn’t correct. Details in NEVDIS can be changed. Quite easily. If anything, if you have one of these vehicles, it’s easier to prove it isn’t a 1960’s era car than anything else, and so registration authorities would be able to cancel the rego. That and it wouldn’t take much for the NSW VIIU unit to establish a more likely correct date of manufacture.
If something sounds too good to be true, it usually is. If you have one of these cars, the simple answer is to get it sorted before it bites you and you permanently lose the ability to have it on the road.