It's fucking open source, this is no different from games with intrusive anti-cheat refusing to run on Linux, except in this case it's not even a different OS.
Ironically, if Graphene would succeed, it would lead to a system that's every bit as locked down as a manufacturer's Android. GrapheneOS would also not allow you to have root etc.
IMO Graphene wants a place at the big player table. They're not in it for user freedoms.