Looking at that page, it cites the rating string "RTA-5042-1996-1400-1577-RTA" with no indication what those numbers mean or why the RTA is repeated. Googling that string, it just seems to be some random fixed token. Why have we got this nonsense?

Also, why is this restricted to only marking up adult sites? There should be an equivalent for marking sites that are specifically designed for children (e.g. educational material) and specifically tested as designed for adults but safe for children (e.g. news).

Without the safe opt-in, this scheme can never work, as the majority of the sites will be considered safe for children when they are not, and nobody will be able to trust it. Better to have an opt-in safe marker, and some enforcement against websites that mark their content as child-safe when it's not.

An example of why you need to force people to opt-in is e.g. HTTPS, which was available for years but only really taken up by banking websites etc. It was only adopted by everybody when it was enforced by the browser. Until website owners are forced to take an action to explicitly mark their content as safe or adult, it simply won't happen at scale.