Where does the article contradict the assertion? Grade inflation does not require any particular relationship between what % correct on exams corresponds to an A grade. It instead generally corresponds to a larger % of students receiving A grades than in the past.
For example, a particular professor might give a challenging exam where the median exam grade is 50%, then curve that exam such that anything above a 40% on the exam is an A, such that the vast majority of students receive A grades. The percent of students receiving A grades might be the same as a different class in which the professor gave easier exams where the median exam grade was 90%. Either one of these 2 classes could have grade inflation, with the vast majority of students receiving A’s.