[2020] Can someone explain this to me? DBG shenanigans?

Back in 2014, the Holiday directive (the first time it was introduced, as Directives were implemented in summer-2014) Holiday Hats were rewards for completing the Tier 3 directive.

These free hats offered no bonus experience.

If you bought a holiday hat from the Depot, it upgraded your default holiday hat (and Auraxium holiday hat) if you owned one, or gave you the new hat if you didn't, and would then give you bonus experience any time you wore it during the holiday event thereafter.