They weren’t starving enough not to take the head and the bones? Either they’re that stupid or the starving excuse is a lie. Any bit of flesh or bone left is proof.
More likely, I would say, that people ballsy enough to do this killed and slaughtered the horse for meat to sell on the black market.
Maybe just not knowledgeable enough about all the edible parts. American Indians considered buffalo tongue a delicacy - lots of valuable fat. But then, they worked a lot harder for a living than most of us.