The same goes with things relating to SEO and since AdSense sits at the intersection between SEO and AdWords, it is not at all surprising that some managers at Google would use the guise of "quality" to juice their numbers.
I don't know if it's true or not, but the story certainly lines up with my experiences with Google over the years unfortunately.
They deal with a lot of spammers and scammers, which is a legitimately difficult job, but they also are a giant megacorp out to make a buck, and that doesn't always mean they do the right thing.
Mostly I bet this gets swept under the rug and isn't investigated, which is a shame.