No. I believe they support Pixels because the bootloader can be locked after install.
I can't understand what you mean with lock Bootloader after installing GrapheneOS. I need to unlock before installing, not lock after.
Locking it after installation keeps your phone secure. If it remains unlocked, then I can get a lot of items off your phone if income into possession of it. It's a security issue. GrapheneOS prioritizes security over privacy more so than other Android builds.