looks like rendering adblockers extensions obsolete with manifest-v3 was not enough so now they try to implement DRM into the browser giving the ability to any website to refuse traffic to you if you don't run a complaint browser ( cough...firefox )
here is an article in hacker news since i'm sure they can explain this to you better than i.
and also some github docs
Who do you think the first / main Attesters are going to be with this proposals? Well, companies that have the mediums to do so and the captive audiences to precheck. Such as GAFAM of which Apple is part and founder of.