There is no value in this "attestation" for me as a user. I want to be able to do whatever I want with the browser (for example, remove ads or block access to canvas and webgl) and I want sites to be unable to know this. And probably this attestation will provide additional fingerprinting signals which is what I don't want.
But software already exists to do this kind of thing for private networks. I really, strongly believe that this kind of functionality has no place on the open web.
This proposal is user-hostile, and could be very dangerous to the future of the web.