So, is the barbarian unarmored defence trait supposed to work with empress garb? Cause it wouldn't be that hard getting AC to 25 without a shield and before other magic items if you spent enough time rolling in the beginning.
As per P&P rules it shouldn't, but I wouldn't surprised if it did.
Note that the 5e barbarian is designed on the basis of standard array/point buy. If you cheat all your stats to 18s it breaks.
This is probably an oversight that comes from the Garb being counted as clothing so characters without armor proficiency can wear it, which is part of the lore of the item. Since the item was designed before Unarmored Defense was programmed, it might've been overlooked that Garb should probably disable Unarmored Defense. Kinda like how Sorcerers couldn't use a certain wizard staff until they patched it.
You should report it and send TA a copy of the save file so they can look at it.
Typos happen. More so on the phone.