Monopoly busting. Ecosystem lock-in. Right to repair. Software patent reform. Privacy and AI regulation.

What do lawmakers even do these days anyway?

From my very basic understanding of it yes. It in effect checks what's loaded against what was served and if there's a discrepancy it does its thing.

Note. If I have misunderstood please someone correct me.

Yes and no. They can freely enforce a specific DNS server and reject any browser with a custom one as "tampered with". Just like they can freely enforce any part of your system being like they want it to be "or else".

All of that can be easily checked via JavaScript, but now if you world use extensions to disable those checks you would not pass the attestation.

So yeah, essentially you no longer have control over your computer, and need to bend over and accept everything the site owner wishes to do.

No, but that only works if the ads are being served by known ad hosts, so you should expect that adtech will get hip to that and proxy their traffic through the same hosts as the content.

That being said, it’s pretty easy to check if a user has network blackholing going on in clientside JavaScript, you just do a test request to a popular ad network and see if it resolves, no special browser support needed.

That's exactly what it is trying to prevent. Basically you, as an user is not to be trusted, so the website and your own computer work together to prevent you from doing anything the site deems inappropriate, like spoofing things, blocking ads etc.