They will require you to only accept Apple Pay in your restaurant, or you will have to remove your app from the app store. :)
https://www.wsj.com/articles/google-loses-key-mobile-payment...
https://venturebeat.com/2018/05/10/apple-pay-credit-card-is-...
Individual retailers do not form an agreement with Apple. Hell, retailers often don't even explicitly and individually support Apple Pay, it just comes through accepting standard contactless payments.