The constituency problem, as Jangari correctly noted, concerns the prepositional phrase "with the solemn precision of scientists articulating chemical equations." The original diagramming indicates that the "we" of the sentence are learning with precision, but it seems much more natural to assume that it is the diagramming that occurs with precision. In other words, the PP modifies diagram, not learned.
That said, there are irritating errors in the book.
The first is that it is unwilling to accept the possibility that the utterance is meaningless.... The other error in the Court's analysis is in mistaking one kind of meaning for another.
(Part 1, Part 3)
The instructions for the writing sections of the the SAT ask the test taker to use the conventions of "standard written English" in finding correct answers. But as I noted in part 1 of this article, the public specifications as to what that means, are vague.