An explanatory note distinguishes joining individual terms from joining complete clauses. In “Zayd and Amr came,” the men share the same predicate. With two clauses, the conjunction joins the statements or their asserted occurrences.
Terms: “Khalid and Sa‘id attended” — both share attendance.
Clauses: “Khalid attended and Sa‘id left” — two different facts are asserted.
Neither construction, merely by using waw, establishes which event happened first. The contrast concerns shared predication versus joining propositions.