It tooks years to implement the whole functionality. They also weren't working on this feature the whole time, but it was on the list. Adding another payment method isn't the same.

Not to mention their current payment method requires play services, which has probably already de-anonymized the user

I agree it's not great to require play services, but it isn't going to always be the only option. It's in beta, so clearly isn't finished.

The users are not de-anonymized, they use a ZKP transaction (https://en.wikipedia.org/wiki/Zero-knowledge_proof). We don't need to have to trust Google, it's the whole point of a zero trust model. Zero trust is required