What grounds the classification of wa-mā qalā as ellipsis?

Supplementary Practice 18: Rhetorical Analysis of Sūrat al-Ḍuḥā and Sūrat al-Sharḥ

• A specific unspoken object can be recovered from the preceding clause
• Every short expression necessarily contains an omission
• Only a resemblance between verse endings
• Simply the presence of coordinating wāw