1. Depends on how it's implemented. It won't identify you to individual platforms if the OS filters on a per-app or per-website basis. And yeah, there would be no dynamic behavior based on age, as that would enable tracking based on age. I don't think any kind of API is the ideal solution though, it's just better than the malicious one being mandated in the Cali bill. Instead of an API, it's simpler and more effective to just have an app installation lock (like sudo on Linux) and a firewall for website blocking with a nice UI in the phone's settings, locked behind a password/pin.

2. Other data points like User-Agent are not required by law, and browsers already spoof user agent by default. I agree that there are other data points we need to address, but the problem in this specific case is the slippery slope of legally-mandated data points. And I don't think winning high profile lawsuits is a real "win", it just exposes problem which we already know in this case. Keep in mind those people can get away with the Epstein files.