What does Muslim add by invoking “the Sunnah indicates…”?

Trustworthy Transmission, the Report of a Fāsiq, and Responsible Narration

• Independent Prophetic support alongside the Qur’anic principle
• Once the Sunnah is cited, Qur’anic proof becomes redundant
• This restricts munkar to defective wording only
• The added report decides only the number-of-witnesses dispute