As always it can depend on who is interpreting the rules. And there are rules that pre-date the ADRs.
When I brought my 67 FB from NZ across to Qld in 2007 the seatbelts - which complied with NZ's rules of the day - required further upgrading. The fronts were already 3-point lap/sash inertia so they were fine, but the lap belts in the back had to be changed to fixed lap/sash.
And the engineers also installed two child-seat fixing points too.
All signed off with a compliance plate affixed in the trunk area.
Maybe overkill when compared to the ADRs 2nd Ed as I read them too, but AFAIAC all worthwhile in the interests of improved safety. With all the mindless idiots on the roads with all the mobile phone and other IT distractions these days I wouldn't have anything less than 3-point belts.