I'd do some basic research about what sandboxing is, it's more an internal software thing. Think about how other apps on your iPhone can't access the keys in a Bitcoin wallet. Apps have separation, different users have separation. A sandbox is just another layer of separation.

It means that Google apps don't have access to the information from other apps on GrapheneOS, on a stock pixel they have total access. You can't track and leak what you don't have access to.

IP address are something different. That's what a VPN is for. But even if they did know my IP, there's far less data to leak. Your phone company (and the govt) has access to all that info anyways, including your location, and a bunch of other information just by you having a phone.

Security and privacy are a spectrum, not an absolute. With GrapheneOS you have more choices of what to share or not. On stock Android or iOS you have fewer choices.