> Supposedly, this is to make sure a browser environemnt can be “trusted”, but it seems Google wants this so they can kill ad blockers.

How would they kill ad blockers this way? I can just use librewolf browser, sites will detect it and not work. But we already have this in form of Widevine DRM. Spotify does not work in my browser without DRM. They can't really force this on google search, because many clients will never support it (older Nokia 3x4 keyboard phones etc).