«زَيْدٌ فِي الدَّارِ قَائِمًا»: the understood “being situated” relates to Zayd; Zayd is the ḥāl referent.
«هَذَا زَيْدٌ قَائِمًا»: the understood act of indicating provides the semantic relation.
This is the book’s explanation of a semantic governor. Do not reclassify every topic or predicate as a grammatical subject/object.