GrapheneOS has https://grapheneos.org/usage#sandboxed-play-services so our users have the option to use Play services too, in a way that will provide more functionality and avoids losing the security checks and key pinning that are missing in microG. We'll be making it easy for users to install via our app repository rather than bundling Google services in the OS.

Google's Play client libraries are still used on CalyxOS by the apps using Play services. The Ads SDK is a fat library and works without Play services. Only the Lite variant of that has a hard dependency on Play. GrapheneOS isn't giving any additional access to Play when it's installed compared to what the client libraries have available.

WhatsApp is clearly a proprietary service too, and CalyxOS is integrating that into the Dialer app. Signal's server source code is not fully public either and went a whole year without even the incomplete releases that are now available again. Both are centralized, third party services integrated in a special way not available to other apps. Isn't that the problem with Play services? It is from our perspective.