1) URE hides ‘administrator’ role from ‘Role’ and ‘Other Roles’ drop-down lists by default.
2) URE exclude users with ‘administrator’ role from the users list by default.
It makes this for users with ‘edit_users’ capability, which do not have ‘administrator’ role.
Thus there is no sense to hide/block ‘administrator’ role via ‘Other roles access’ add-on. ‘administrator’ checkbox is disabled for this reason.
