A rare category consists of people whose personal name is itself in the form of a kunya. It would be mistaken to insist that this form must conceal a different personal name.
Another category arises when sources disagree about a narrator's kunya. One biographical record may give a particular kunya while another provides a different one. That disagreement does not by itself prove there are two persons.
Distinction: having a kunya-shaped personal name concerns the form of the name; disagreement over a kunya concerns conflicting identification reports. These require different investigative steps.