What is lost by treating «فَوَسْوَسَ» and «قَالَ» merely as synonyms?

Faṣl: Substitution, Quasi-Complete Connection and Quasi-Complete Disjunction

• The object becomes negative
• It overlooks the implied question-and-answer structure
• It changes past-tense inflection
• It removes the fāʾ in the Qur’an