Multiple designations create two opposite risks. A known narrator may be misclassified as unknown under an unfamiliar label. Alternatively, several appearances of one person may be mistaken for support from several independent narrators, exaggerating the number of routes.
Imagine a transmitter called “ʿAbd Allāh,” “Abū Muḥammad,” and “al-Baṣrī” in different chains. Once independent contextual evidence establishes that all three labels identify the same person, the three appearances must not be counted as three separate transmitters. But that identification itself requires evidence.
Good criticism establishes not only the label but the actual number and independence of the persons involved in the chain.