Ok. If they had never added the Spriggan mount to the Mogstation, and you never knew it even existed, would you feel cheated by this seasonal event?

Then consider that the mount is an additional, optional, glamour peice. Just like everything else in the store.
Did you freak out when they added the whale? Or the bike?

Then question why you're making a big deal about this and even going to such lengths as harassing players who use it.