LineageOS also discourages and doesn't support replacing the core of the OS with a rootkit providing persistent app accessible root. GrapheneOS is no different from LineageOS in that regard. People do this with GrapheneOS regardless of our strong recommendation not do it. Our reasons for discouraging it aren't vague. It very directly harms the security model and is not a good approach to implementing any of the features hacked together through it. Those features should be properly implemented to fit within the overall approach taken by GrapheneOS. Giving root access to a huge portion of the OS harms security even if you never use the feature. It does not mean you can't do it, we only recommend you don't.