Grapheneos.org explains how the sandboxed GPS minimizes what it can collect. The highly promiscuous standard implementation of GPS has massive access to your device with limited and uncertain abilities to restrain what it can collect. All apps in Graphene are treated as hostile with fire grained firewall abilities. The sandboxed GPS from Graphene is implemented as any other app and only needs network access to deliver notification.
I created an anonymous Google account and only give it network access until the day some of the apps I need. Google only knows that someone from an IP address is getting notifications for those apps that use it. Once these apps switch to unified push or web sockets to deliver notifications, I will remove GPS.