Literally none of what you said is true.

Go read the GPLv3 license and/or ask yourself how Linux distributions are able to ship a mix of GPLv3, v2, MIT, BSD, etc licensed software all in the same image.

GrapheneOS may or may not have a policy against shipping GPLv3 software (I don't know), but if they do, it's a political or business decision, not a restriction imposed by GPLv3.