When the circumstantial clause begins with a pronoun that itself serves as the nominal subject, wāw becomes especially important in marking the nominal sentence as an accompanying circumstance.
«جَاءَ زَيْدٌ وَهُوَ يُسْرِعُ»
Zayd came while he was hurrying.
Here huwa is a nominal subject and yusriʿu its predicate; the whole nominal construction serves as ḥāl. This differs structurally from “Jāʾa Zaydun yusriʿu”, in which an imperfect verb describes a concurrent activity directly. The presence of wāw is linked to sentence structure, not simply an ornamental choice.