"Turn on an ad privacy feature" is the title of the blocking modal in Chrome that tries to get me to turn this on.

But of course, it is the opposite of a privacy feature. A privacy feature would reduce the amount of personal data being shared. This increases it.

This undermines your claimed Privacy goal number 4, and reveals the actual intention of this API proposal. This is after all a Google proposal and the current UX is a Google implementation, and Google has an obvious interest in tracking-based ads. This proposal should be rejected.