Indeed it seems like a bug ...
Concidering Roll20 description, it seems it should do nothing once you have 16+ ... and it should cap it on 16, no matter what AC reduction effect you have active ...
So, usefull when you dont have much AC and are fighting in Acid pool ... i gues?
I know its often recomended to use for Shapeshifting Druids, since you adapt that animal AC.
But for Barbarian, i would dare to gues it "is suppose to work" same as with Lizardfolk Natural Armor and Unarmored Defense ... you have to pick wich you want to use.
