[jasode]

>The data is sent from the advertiser to the ad platform, not from the publisher to the ad platform.

Then we're talking about different things. This thread has packet filtering to prevent user behavior being sent to Google. For example, see recent thread about Google's click tracking: https://news.ycombinator.com/item?id=28672625

The key is that click choice data on Google's search results page is never seen by advertisers so your explanation of "next gen tracking is by advertisers calling APIs to ad networks" -- isn't relevant to that scenario.

Then another level of tracking underneath Google's visibility of click behavior on its own search page is the website (publisher/contentcreator) recipient of the click. Whether any advertisers see this downstream click statistic on an ad network depends on the particular website. E.g. a content creator website might have tracking that sends data to Google domain "googleanalytics.com" -- but no advertisers.