What distinguishes the pronoun in “جاء زيد وهو مسرور” from a pronoun of affair?

The Subject of Predication: Pronouns of Affair, Iltifāt and Departure from Expected Expression

• Both must be pronouns of affair
• The former refers to Zayd; the latter is clarified by a following clause
• A pronoun of affair is always plural
• An ordinary pronoun has no referent