I would argue the distinction between my own user and root is not meaningful when they say "all files by default". As my own user, it can still access everything I can on a daily basis which is likely everything of importance. Sure it can't replace the sudo binary or something like that, but it doesn't matter because it's already too late. Why when I download and run Firefox can it access every file my user can access, by default. Why couldn't it work a little closer to Android with an option for the user to open up more access. I think this is what they were getting at.