> If you have the UI layer able to grant root access, it has root access itself and is not sandboxed.

The same is true even of an operating system such as QubesOS. And it's a minimal risk.

Not providing optional root access on GOS makes it only useful if you have a constrained application in mind for the phone. I don't have time to compile GOS with root so I just use LineageOS instead.

It's useful for general use just fine.

But you could always do both. Compile it, but preinstall a specific set of apps as root, no su.