For other events, like the Valentione's event last year where all we got was the moogle cap, then yes it is silly that it was the reward they chose to give out when some races can't equip it.

For Heavensturn in particular, they always give animal helmets. This is the year that the set of twelve is complete. They're not going to make something that doesn't match the other eleven.

Maybe next year they'll move on to a new design that everyone can equip.