I heard Hermes DFS is different from the usual stores we have in the country. They are run by a different operation. And no, they can't sell Birkin. Only recently they are selling kelly
In Europe, airports are not allowed to sell birkins or kellys in any size.
I think another tpf mentioned that there is kelly available in Hong Kong airport but that is because there is no tax in that city so slightly different scenario, not sure about other countries.