I have an Android phone and have every single one of my credit and debit cards from 7 different banks in Google Pay. Don't need to use the bank app for any of them.
EDIT: to be clear, currently on Android any app can handle NFC payments, not just Google Pay. Banks could easily force people to user their apps, but that's not happening.
EDIT: to be clear, currently on Android any app can handle NFC payments, not just Google Pay. Banks could easily force people to user their apps, but that's not happening.