Looking for the same answer here...One feedback for the Google Ads team : this new setting was enabled silently, and default value was set to not-off, which means some audience expansion level 1 or 2 out of 5. (It's a sliding scale in the UI). Silent updates like this breaks existing systems and should be avoided by Google. In the past, a similar thing happened, where all mobile traffic was enabled (again, silently for currently active ad groups), whereas currently enabled ad groups specifically had a negative targeting for all mobile apps. Remember the
adsenseformobileapp.com setting? That was retired, but then all ad groups which previously were configured NOT TO SERVE on mobile app, suddenly started reaching mobile apps.
These could be simply overlooked as "default values", but has dire consequences for active campaigns. When Google introduces a new setting, the default for new adgroups or campaigns is one thing, but applying the same default to currently live camapaigns and ad groups is an entirely different animal. What should Google do? Preserves the old state of the current campaigns and ad groups.
So in this case, "Similar Audience" targeting was off for all our campaigns, and therefore the new "sliding scale" should have been off for these. Now we have a problem in hand to turn all of them off. But how do we do that via the API?