نحو: جاءني زيد وهو راكب
For example: Zayd came to me while riding.
‘Zayd’ identifies the person; «وَهُوَ رَاكِبٌ» describes his condition when arriving. Identification of the individual and description of a circumstance are distinct. Replacing the name with an indefinite noun changes the identification, even if the circumstantial report remains.
«جَاءَنِي رَجُلٌ وَهُوَ رَاكِبٌ» reports that a man came while riding, without identifying him by name. A shared descriptive detail does not make the two subjects rhetorically equivalent.