I find this comment to be rather sad.
In addition, there's only a loose relationship between getting a very good grade in a course (as opposed to a good-mediocre one) and getting breadth knowledge out of the course. To believe otherwise would be to satisfy tendencies of grade inflation. For example, an A in a course was originally supposed to mean an excellent performance beyond expectation. To get an A in every single course should signal that you are either 1) extraordinarily dedicated to your school work and extremely bright or 2) the school is handing out an A not for extraordinary work, but only good work. In light of this, the most reasonable grade distribution for a bright, dedicated student would be a very strong (hopefully A level) grade distribution in their area of specialization with a good but not as extraordinary distribution in their breadth subjects.
It was interesting that you noted me as focusing on CS like vocational training when I actually take pride in my choice of courses as true liberal arts education. For example, while I am an engineer CS major, I will have taken enough courses in the physics and philosophy departments to almost qualify for a minor in the fields. Simply because I am unable to dedicated my time to all of my varied classes at once does not mean that I do not participate in number of different liberal arts.
Many had passed the A.P. exam, but had either been advised to take the college course as a way to deepen their knowledge or had to because their exam score did not meet departmental requirements. This group gave us an opportunity to see how A.P. students fared in college science, since passing an A.P. exam is presumed to mean that they had mastered a college-level course.
We found that students who took and passed an A.P. science exam did about one-third of a letter grade better than their classmates with similar backgrounds who did not take an A.P. course. Even a score of 5 on an A.P. test is no guarantee of a college grade of A in the same subject.
First, passing an AP exam (3 or better) is only presumed to mean that they mastered the course at the less selective schools. It says in the preamble that the most selective schools recognize that a 3 or 4 is not good enough for college credit.
He then went ahead and decided that he would compare people who didn't get a 5 on the AP test with people who had never taken the course and decided that the grade difference meant that APs don't mean anything. It's like taking a group of people who failed a test the first time, giving it to them again, and then being surprised when the fail again. (Note: They didn't really fail, they just failed to be in an upper percentile of the class, which would be expected if they didn't know the material.)
I also find it hilarious that he expected everyone with a 5 to get an A in the course. I know a bunch of subjects I could have got an A in had I cared less about my CS courses.