I'm not sure if you are aware, but the number is stored in Wallet. Of course I don't know how a waiter or convenience store employee will handle you showing them a number that's not on a card. Some may not accept it if they are old school.
I'd like to know if users on the iOS 13 public beta will be able to sign up. It would be kinda crappy if not.
ApplePay displays only the last 4 digits of your actual card. You could have a problem if the number required.