The Qur’an’s inimitability (iʿjāz) and challenge (taḥaddī) concern the revealed Arabic arrangement, its communicative force and the meaning it signifies. If the transmitted verses were entirely excluded from the term Qur’an, the language of challenge and public revelation would become difficult to account for.
The opposite inference is also unwarranted: because the challenge concerns articulated wording, it does not follow that the divine attribute is originated whenever a human recitation occurs.
One can recognize both the inimitable revealed arrangement accessible to people and the eternal attribute of speech, while keeping their respective claims distinct.