What is the function of «yaʿnī Ḥammādan» after «Ibn Zayd»?

Reports of ʿAmr ibn ʿUbayd: Attribution, Conflicting Accounts and Evidence of Criticism

• To identify Ibn Zayd as Ḥammād
• To prefer Ḥammād’s judgment over a Successor’s
• To preserve a hearing formula for Ibn Zayd
• To make Ḥammād an additional distinct narrator after Ibn Zayd