A charge on Apple Pay is not due until the last day of the following month, so you are not out anything when the charge goes through unless the backordered item doesn't come in until after the due date.Thanks, that's good info.
"We accept payment via Apple Pay, PayPal & PayPal credit. We also accept payment via Google Pay on Android devices and apps only. Payments processed using such apps will be charged immediately (as opposed to when your order ships)."
Moral: it's good to be very aware of your bank statements, but you also need to be aware of the policies of the companies from whom you are making purchases.