your understanding is incorrect. Apple has explicitly stated that the transaction is 100% between The Merchant, Your Bank, and you. Apple does not receive a copy of the transaction, they don't know who you've shopped with, and that they don't know that any specific transaction has happened.
The only thing Apple does is act as the facilitator to getting the device-specific account number in to the phone. So Apple could know which credit cards you have setup in your device and that's about it.