[Client?] Potential ward skin issue

Hi, I have noticed a potential issue or bug which only happens at certain times of the year... I have been playing since June 2013, and I have noticed that during the limited time the Gingerbread Ward skin is available each year, I am able to use it even though I have never bought it or had it gifted to me. When it is not available in the shop, I do not have access to it. I assume this is a bug? To my understanding, I should not have access to that ward skin at all, let alone only part of the time. There has apparently been discussion about this in the past according to a Google search I did, but I am of course curious.