A prophetic claim raises two separate questions: (1) did this person actually claim prophethood? and (2) is there sound evidence that the claim is true?
The fact of Muhammad's ﷺ claim, his call to monotheism and his presentation of the Qur'an are transmitted through extensive testimony. The Qur'an's inimitability and other signs have a distinct role in establishing the truth of that claim.
Transmission of a claim and verification of the claim should not be conflated. Reliable history shows what was asserted; a further evidential argument addresses its truth.