It's probably about a tie with plumbing. The reality is the whole country does a weird cold-war type arrangement where no one asks too many questions at Bunnings.
Which is absurd because of course it's essentially the worst possible outcome: people either can't afford necessary work and so never do it, or figure it out and get it done to varying levels of quality which they then never talk about or show anyone because there's no way to get stuff approved.
It's wild to me that you have American DIY channels where people want to put a new circuit into their switch panel box, and just call up the local code office to check what they need to show to get it signed off - then go and do that (also, American switch panel boxes look like such a better system then what we do in residential Australia).