The source also places a genitive complement after siwā and sawāʾ.
«جَاءَنِي الْقَوْمُ سِوَى زَيْدٍ»: Zaydin is genitive in iḍāfa.
The final alif of siwā does not show its case ending; traditional parsing uses an estimated case.
Follow the source’s exceptional use of sawāʾ here rather than conflating it with every everyday meaning of “equal.”