خَالِدٌ صَادِقٌ وَهُوَ أَمِينٌ.
Khalid is truthful, and he is trustworthy.
Both clauses predicate closely related virtues of one person. The conjunction places them within a shared frame and provides a defensible reason for waṣl.
It is equally mistaken to make “wa” invariably temporal: it does not by itself impose sequence. The sentence does not say that truthfulness came into being before trustworthiness.