Yes.
Firstly, any claim that Google apps circumvent being blocked from the internet via Google Play Services is hypothetical. We know they can, not that they do.
If internet access is revoked for all the Google apps, then there's no way for them to communicate with Google servers, hypothetical or not. No other app/service on Android (AOSP) / GrapheneOS will help these apps circumvent their internet restriction even though Android is developed by Google.