All of this has already been explained to fsflover in detail numerous times, but for any onlookers here are some of the project's thoughts on the subject of hardware attestation:
On the subject of root, it completely breaks the security model of the OS, and for very valid reasons they have no interest in having official installations with widely varying security models.
They also have no opposition to people creating their own forks to do so, and they publish comprehensive build instructions:
https://grapheneos.org/build