I see that, after people raised a whole bunch of issues with the proposal, there's a new message on the Web Integrity API repository: "An owner of this repository has limited the ability to open an issue to users that have contributed to this repository in the past." So the Google engineers' response to people pointing out the defects of the proposal was to shut down people's ability to raise issues with it. It's a good little preview of how they intend to treat the web's users.