Unfortunately it is so.

It's explained here by nostr:npub1gd3h5vg6zhcuy5a46crh32m4gjkx8xugu95wwgj2jqx55sfgxxpst7cn8c

https://discuss.grapheneos.org/d/475-wallet-google-pay

No GPay/Wallet cannot be made to work on GrapheneOS and is a limitation in so far as Google Pay/Wallet requiring full SafetyNet compliance. GrapheneOS can pass BasicIntegrity but the OS cannot pass ctsProfileMatch as that would require GrapheneOS to be whitelisted by Google. Google Pay/Wallet requires both.

Before the idea of bypassing the checks is brought up, as some other OSes or Root methods might allow, please read the following: https://nitter.net/freechelmi/status/1553326311854276608#m