How should wāw in 99:8 and 100:7 be distinguished?

Supplementary Practice 25 — Comparative Rhetoric of Sūrat az-Zalzalah and Sūrat al-ʿĀdiyāt

• The first is an oath wāw and the second a circumstantial wāw without a pronoun
• Both wāws negate the statement
• The first is superfluous and the second invariably an oath
• Both coordinate, but the first links contrasting conditions and the second a related testimony