Does Google advertising offer paywalls and forced adblocking services? Or does the presence of a paywall and forced adblocking tend to imply the use of something other than Google ads? (Honest questions; I have never used any advertising and have no idea what they currently offer.)

Depending on the answer to those questions, it may be the case that knocking those sites out of the feed would statistically drive revenue to sites more likely to use Google's ads, in a way that would give them total plausible (if not simply "true") deniability.