فَالْهَمْزَةُ لِطَلَبِ التَّصْدِيقِ
Hamza is used to request assent.
Hamza is capable of seeking both taṣdīq and taṣawwur. In the first use the whole proposition requires assent; in the second, one component of an understood relation needs identification.
The mere appearance of hamza does not prove that a yes/no answer is expected. Two alternatives joined by am may show that the speaker wants one component specified, not the proposition confirmed.