In the Qur’anic expression containing “quruʾ,” the debate is not over whether the verse exists, but whether the shared word indicates menstruation or periods of purity. A text can be transmitted with certainty while some of its lexical possibilities remain open to juristic disagreement.
Selecting one sense requires linguistic usage, context, and supporting evidence. Familiarity alone is not proof. Thus certainty of transmission must not be equated with certainty of a specific interpretation.