Your last paragraph, and particularly the last sentence, epitomizes what is wrong with your whole thesis: the ultimate goal of the testing (and education itself, for that matter) is not to find people who can "do well on essays"; it is to develop analytical thinking.
That assumption lacks justification when the scoring does not actually measure analytical thinking. Any statistical evidence for it is suspect as a predictor of future outcomes when a high score can more easily be gamed than 'honestly' achieved.
Scoring is not the point here; the analytical thinker is gaming the test to pump the score, thus proving they are an analytical thinker. Not a statistical argument; a suggestion that the screen works, when it is abused. Because it is abused.
