I think you're making a mistake here; you're assuming that somebody does read the SAT essays in order to mark them. There's ample evidence (promulgated by Les Perelman, especially) that this isn't the case. Start with the realisation that markers are recommended to spend 2-3 minutes on each essay in total! Here are a few links that come to hand:
http://www.insidehighered.com/news/2007/03/26/writinghttp://www.nytimes.com/2005/05/04/education/04education.htmlhttp://www.nytimes.com/2012/04/23/education/robo-readers-used-to-grade-test-essays.htmlHonestly I would advise anyone to completely ignore anyone's SAT essay score; it isn't evidence of anything interesting.