Existing systems which evaluate each passage separately against the question would view each passage as having a similar degree of support for either hypertrophic cardiomyopathy or aortic  stenosis as the answer to the question.
these systems lose sight of a crucial fact, namely, that even though each passage covers half of the facts in the question, (2.1 a) and (2.1 b) cover disjoint subsets of the facts, while (2.2 a) and (2.2 b) address the same set of facts.