Can’t say I blame them.
As but one possible example. Common infrastructure to handle whitelisting would probably go a long way here. Just being able to tag a phone, for example, as being possessed by a minor would enable all sorts of voluntary filtering with only minimal cooperation required.
Many sites already have "are you 18 or older" type banners on entry. Imagine if those same sites attached a plaintext flag to all of their traffic so the ISP, home firewall, school firewall, or anyone else would then know to filter that stream for certain (tagged) accounts.
I doubt that's the best way to go about it but there's so much focus on other solutions that are more cumbersome and invasive so I thought it would be interesting to write out the hypothetical.
Seems like right now the Aus Government isn't sure how they want it to work and is currently trialing some things. But it does seem like they at least don't want social media sites collecting ID.