Fully upgrade Byzantine Camel Rider mercenaries receive the stat bonus for the Abbasid “Camel Barding” armor upgrade (+2 melee/ranged armor), but the visual armor upgrade does not apply. They do receive the Camel Shield stat bonus AND visual.
Byz Mercenary Camel Riders with all stat upgrades but missing Camel Barding visual:
Here is a photo of the Camel Barding upgrade