I am not sure Apple can differentiate Apple devices over HTTP except UA header. Maybe they can develop a proprietary streaming protocol but is it worth?
yes, for example with device fingerprinting. the Electronic Frontier Foundation has a nice test page online: https://panopticlick.eff.org/
however apple could apply a much simpler filter by checking whether the screen size fits the exact specs of their iphones / ipods and ban any other devices.
then again, you might always access the source directly, circumventing the need for js entirely.