A ḥāl qualifies a prior predication through the state in which it is realized. جَاءَ زَيْدٌ already states that Zayd arrived; رَاكِبًا restricts the event to an arrival in the condition of riding.
Thus a circumstance should not be treated as if it were automatically a second independent judgment linked by ordinary coordination. Even when a circumstantial expression is internally a full clause, its discourse role can remain subordinate to the main event.
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Appendix to Faṣl and Waṣl: Circumstantial Clauses, Wāw and Pronominal Linkage
A ḥāl qualifies a prior predication through the state in which it is realized. جَاءَ زَيْدٌ already states that Zayd arrived; رَاكِبًا restricts the event to an arrival in the condition of riding.
Thus a circumstance should not be treated as if it were automatically a second independent judgment linked by ordinary coordination. Even when a circumstantial expression is internally a full clause, its discourse role can remain subordinate to the main event.