What distinguishes ellipsis of the subject from identification by iḍāfah?

The Subject through Iḍāfah and Indefiniteness: Rhetorical Purposes

• Iḍāfah always deletes the pronoun
• Ellipsis always requires a proper name
• Ellipsis leaves the subject unexpressed; iḍāfah retains and identifies it
• Both omit the subject entirely