So what you meant was, they can't wear the specific BiS (per era) robes.
Here's another robe anyone can wear,
Guardian Robe. (not saying this is any good on a cleric)
At any rate, Dwarves and Halflings don't have robe models, so they will all just look like tunics of the corresponding color and don't fit his request for cool pieces. (visually, I assume, based on his mention of scarab)