googlepay/com.siddharth.kmp.provider.googlepay/GooglePayGateway/availability

availability

open suspend override fun availability(host: PaymentHost): WalletAvailability(source)

Whether a Google Pay button may be drawn, asked before anything is drawn.

isReadyToPay answers one question - can this device pay right now - and folding its false into the same bucket as "Play Services is missing" is what loses the difference between a user who needs to add a card and a device that can never do this at all.