I'm part of the Twin Adders and I decided to purchase the 6000 Seal "Gridania Barding". There was Half-Plate for 4000 and the Full Plate for 6000 and then Crested for 8000(not level 44 yet).
When I went to equip it just shows the default Twin Adders barding there not the new one and my Chocobo looks the exact same as it did before.
EDIT: Derp it goes into your bags and you need to interact with it first.