Sandboxed Google Play:
"Since the Google Play apps are simply regular apps on GrapheneOS, you install them within a specific user or work profile and they're only available within that profile. Only apps within the same profile can use it and they need to explicitly choose to use it. It works the same way as any other app and has no special capabilities. As with any other app, it can't access data of other apps and requires explicit user consent to gain access to profile data or the standard permissions. Apps within the same profile can communicate with mutual consent and it's no different for sandboxed Google Play."
I installed grapheneos yesterday and installed the three google play apps because I want banking apps and whatsapp (which is my main source of communication). I wanted to compare google camera and grapheneos camera, so I installed google camera from the playstore and and gave it access only to camera and microphone (declined network too). But right after I took a photo, it showed me an option to share it with whatsapp. How did it know that I had whatsapp in my phone. The obvious answer would be through google play services but if it can access that, what does sandboxing even mean?
I'm sorry if this is too basic of a question. I'm just trying to understand grapheneos and it's features more.