GrapheneOS isn't rooted. It's caused by their anti-tampering code being buggy and recent releases of the app wrongly detecting secure spawning as tampering. We have a per-app secure spawning toggle due to these issues and that works around it.

GrapheneOS doesn't give you root access.

The OS is designed to offer privacy and security guarantees, which root access breaks, so they don't offer it.

A normal GrapheneOS installation uses Android Verified Boot with a locked bootloader, and does not give the user root access. Google's Play Integrity cannot be used to verify the integrity of the OS (as GrapheneOS is not approved by Google), but equivalent verification can be done using standard Android APIs and GrapheneOS's public keys.

I wonder do you have administrator access on your Windows/Mac/Linux?

Because your argument sounds like you gave the admin password to someone else to prevent yourself from tampering with your computer for the security reasons