I suspect there are more than just one combination of frontend and backend for Apple/Google Pay depending on how you're paying, masked behind that act of you presenting the device and store presenting the reader.

So I think there can be cases where "payments" (or promises thereof) can be made, while money withdrawn from banks notwithstanding, e.g. queued in an intermediary entity and manually resolved on request, in which cases the payment gateway might want to pattern detect and shut down such cases.