If I remember correctly, the idea is to block ads that don't conform to the standards set by the Coalition for Better Ads [0]. Google is (as you can expect) a member of this coalition (just like Facebook and many other companies [1]).
I get Google ads on mobile that flash and mislead. Virus Scan! Battery Scan! Clean Your Phone! With yellow and red. So at least on Android, Google serves tons of shit deserving blocking.