>not a fan of the government approach of "everyone must prove their age online now", which I believe is how the AU law is done

This is not how the law is implemented. The vast majority of verification is being done by 'age inference', ie analysis of the content the user consumes or posts to infer likely age. Only accounts suspected to be children by the inference process are being required to verify or have the account disabled. In practice, the inference process means very few accounts are required to provide any proof of age. Personally, I haven't been asked to verify by even a single website.

The age inference process is described on this page under 'What is Age Assurance?' https://www.oaic.gov.au/privacy/your-privacy-rights/social-m...