The huge difference is that these laws make that data flow to the sites, which are then in control of the go/no-go decision. This is another data point of identifying information being leaked to the surveillance industry, and people who opt out and use secure browsers (that don't leak such info) will be denied access, or put in a legally fraught position when programmatically declaring an incorrect age (eg 1970-01-01) to interoperate.
The open society free association version is where information only flows from sites to user agents. Sites declare who they consider themselves suitable for - "appropriate for under 18", "appropriate for under 13", "contains moderated user generated content", "contains unmoderated user generated content", "uses algorithms meant to increase individual engagement (ie addiction)" etc. The browser then makes the choice based on its parental control settings.
(note that unlike GP comment there is no need for a "government list". site self-assertion handles the technical implementation perfectly, browsers with parental controls enabled don't display sites that don't include tags, and legislation requires a good-faith labeling of sites over a certain size so sites don't simply try to push some fiction saying that every user must be over 18)