With Dire Wolf’s Band equipped, which causes Grizzly Rage to affect your Werewolf Form instead of your Werebear Form, activating Grizzly Rage seems to remove the ability from the skillbar, along with companion abilities as well.
Haven’t tested this thoroughly, but I’ve noticed whenever I activate Grizzly Rage with the Dire Wolf’s Band equipped, it completely removes Grizzly Rage and my Wolves active ability icon from my hotbar, making them essentially unusable (as if they were unequipped).