Apple claims “When you make a purchase, Apple Pay uses a device-specific number and unique transaction code. So your card number is never stored on your device or on Apple servers. And when you pay, your card numbers are never shared by Apple with merchants. Your purchases stay private.”
But they save your cards in the apple wallet app, so how are they saved if they don’t store your details on their servers or on the actual apple device? I have a theory but I’m not sure.