Quote Originally Posted by Felis View Post
They are part of the Mainstory if a mainstory quest (those with the meteor icon) tell you to kill them. For now they (Garuda hard, Ifrit hard and Titan hard) are only required to be cleared, but not part of the mainstory itself.
Only at Moogle King the primal hardmodes begin to be also the primal storymodes.
Oh come on. While they are not part of the main story, they are still required to continue the main story. As a result they are part of the main story, even if it is "unofficially".