Regulators can't verify every single Facebook ad. So, they take a sample. Facebook is creating a Potemkin village - trying to provide a clean sample. It suggests they don't believe that a wider sample would pass muster.

It's more like if the health inspector found e coli in the spaghetti, so Facebook threw out the spaghetti then said "trust us, you don't need to check the macaroni, it's fine."