In a common grammatical analysis, a separating pronoun (ḍamīr al-faṣl) does not take over the syntactic role of the main predicate. In «Zayd huwa al-qāʾim», «al-qāʾim» remains the expression whose meaning is predicated of Zayd.
Certain sentences admit alternative grammatical analyses, so it is unsafe to classify every occurrence of a pronoun by appearance alone.
The rhetorical question remains whether the speaker is aiming at distinction, emphasis, or restriction, and which of those functions the context brings forward.