There is a middle ground where they only audit the ads on the big clients. If you are say a top 10 Reddit client by usage it is going to be hard to get away with not showing the ads.
I've undergone audits for "Sign in with Facebook" usage in the past on a small app (~50k FB auth'd users), and it was enough of a spot-check that they probably catch egregious mis-use with not a lot of effort.