Just because the CA or the intermediate says EV doesn't mean that they only issue EV certs. The CA we use at work will issue certs with their EV root when we need compatibility with older installs, they only had their EV root cross signed.
Yes, but EV is not the same as identity validation. That's another variant of certificates that was only introduced because identity validation alone is so bloody useless.
Couldn't you also use HPKP to pin the EV-only root?
Doesn't protect against a hacked/rogue CA, but against someone getting access to your DNS/mail/web server and getting a useable certificate from a only-domain-validating CA.