Is the ESRB broken when it comes to South Park?

How does South Park: The Stick of Truth receive a Mature rating, but Grand Theft Auto: San Andreas received an Adults Only rating after Hot Coffee was discovered in its game files. This is just mind boggling.

I can't wait to play The Stick of Truth, so I'm not hating on it. I'm just wondering if people look at South Park and are just not phased by it anymore, or if the timing of the releases has more to do with it.