Can someone explain why the Armoire in the inn room is so stubborn and restricted?

We can put our class lvl 50 gear in there under Artifact that we get from our end job quests.
But we cant put our AF2 Gear in there we get from trading in myth, let alone darklight gear.

We can put all previous seasonal gear in there from stuff such as the Reindeer Gear but we cant put our santa/snowman gear in it.

We can put Achievement items we get from Achievements in there but we cant put in items from EX HARD modes in it.

Is there a reason why they haven't just allowed us to put any gear in it?