D4D, Symon
I don't know why you both have such a problem dealing with the fact that the ADRs, ASs and other legislative instruments govern what is permissible with cars, trailers, buses, trucks, etc; and that insurance companies have their own rules; then the various police forces have own their interpretation/s of what those laws mean (usually pretty basic, and often wrong, IME). Then there are the interpretations courts put on things; then various State and Federal governments legislate again, extending or clarifying laws in the light of all these things and more. So the cycle continues ...
If you think that this leads to a consistent and sensible set of rules, good luck.
What it does lead to is a set of relevant dates, as they are generally known legally (whether applying to Superannuation laws, or any other, such as motor vehicles and the like). What one is legally obliged to do is to keep one's vehicle in a roadworthy condition, and this requires one to ensure that it complies with the laws pertaining under the rules that applied at the relevant date that is applicable to the compliance plate affixed to the vehicle, be it a car, light truck, trailer, or anything else that comes under the governing laws and regulations made under those laws.
The laws and regulations are what they are. We all need to be mindful of what they require, and abide by that. Venturing outside of those requirements, even if it seems to be "better" can be fraught, which is why I implore people to check with the authorities and their insurer/s (and not take my word for it!). They make the final decisions, and better to get it out of the way before anything unfortunate occurs than try to argue the toss in court after the event. I always check with both the authorities and (specially) my insurers about anything and everything. This leads to far fewer problems in the long run.
br to you both, RB.