I’m not sure, but even with jailbreaking, iOS isn’t certified UNIX. It doesn’t have a command line shell built-in that you can access easily like macOS.

So I really meant “locked down” in the sense that you’re not getting easy access to command line interface that can access system files without jailbreaking/rooting first.

I do think jailbreaking and rooting is easier than it used to be, but I don’t mess with iOS devices much.