Comment by palata
I think you're confused.
I you run GrapheneOS, it is an open source platform built on top of AOSP (the Android Open Source Project). Part of the security model is that you don't run as root. I am an advanced user and I don't want to run as root on my phone, I am happy with GrapheneOS as it is distributed.
Now if you want to be root, you can install an OS that allows you to be root. Just like I unlocked my bootloader, installed GrapheneOS and relocked my bootloader, you can do that and install whatever you please. I will keep using GrapheneOS because that is the most secure OS I can find for my phone.
The problem, IMO, is not that "some OS are opinionated and don't give you root access while other OSes do give you root access". The problem is that on many phones, you are not free to install the goddam OS you want (e.g. because you can't unlock or relock the bootloader).
Root used to just mean knowing an admin password and rarely using it on desktop platforms for making local changes. It's changed definition for mobile if it now means just being able to run and auto-update apps from fdroid or run an app without the attestation of the company that supplies the OS, which in the worst cases takes away control completely from the user.
Mobile platforms and developers solely supporting their attestation should allow other forms of self attestation that the users want. I don't think I'm confused about anything, and I don't need to muddy the definition of security or root to argue having control over my data and apps on platforms I want to use.