brandy078 WhatsApp can gather less information about you in GrapheneOS than on stock Android. GrapheneOS offers the ability to set up a Contact Scope, which means WhatsApp can only read the contacts and phone numbers you allow it too, not all your contacts and contact data. You can also set up Storage Scopes, so WhatsApp cannot read all your media files, only the files you allow it to. Both of these things together will make it much more privacy respecting to run WhatsApp on GrapheneOS than it would be on stock Android.
WhatsApp can still communicate with other Meta apps you have installed, to share account information. An Application Scope feature is planned but not available yet. Such a feature could make WhatsApp believe no other Meta apps are installed. WhatsApp will also still always be able to obtain identifiers for your Google services since it needs Google services to function.
Of course all interactions with the WhatsApp app itself can still be gathered by Meta, including information about who you communicate with, when, and theoretically what you write.