Does uninstalling Xcode with the --all option remove everything?

Question

The documentation says:

To uninstall Xcode developer tools on the boot volume along with the directory, from a Terminal window type:
$ sudo <Xcode>/Library/uninstall-devtools --mode=all

To remove the underlying developer content on the boot volume, but leave the directory and supporting files untouched, from a Terminal window type:
$ sudo <Xcode>/Library/uninstall-devtools --mode=systemsupport

My confusion is because the first option doesn't mention anything about removing "the underlying developer content".

Is the second option a subset of the first? Or do I need to run both to completely remove all traces of Xcode from my system?

Is this "underlying developer content stored in the Xcode directory or some place else? If it's in some other place, it sounds like it would be hard to remove if you have two versions of Xcode installed.