When I joined Google in 2015, one of my work buddies / teammates was someone who had transferred in from having spent nearly ten years on the Ads side, from a GCAS (Global Clients & Agency Solutions). This org doesn't exist in the same form anymore, but at that time it was the pinnacle of Google's ad sales, with white glove treatment for the top xx global spenders (advertising agencies, who consumer products firms, a couple of travel aggregators -- you get the idea). We talked a lot, about a lot of things, and one tidbit I crisply remember was her noting that it was common knowledge that Ads had the ability to "turn the dials" on various things, including in Search, to affect business metrics.

Reading Ed's post reminded me of this, and whether (or to what extent) it's true, it certainly was conventional wisdom at the time.