The second requirement is familiarity with contextual reports that explain the force of certain descriptions, indirect references or strong rebukes. Occasionally the target or intensity of an expression becomes clear only from pertinent background.
This need does not make every narrative equally reliable. The reporter, content, chronology and fit with the text still have to be examined so that helpful context can be distinguished from unrelated anecdote.
Together, the two requirements concern necessary incident-specific knowledge and evidence that clarifies the intended force of the verse—not exhaustive memorization of every transmitted story.