When an app is first opened it needs to validate the digital signature with Apple. So they do definitively know the volume of apps a developer has sold. Store

When an app is first opened it needs to validate the digital signature with Apple. So they do definitively know the volume of apps a developer has sold. StoreKit API likely phones home as well: https://developer.apple.com/support/storekit-external-entitlement https://developer.apple.com/support/storekit-external-entitl...