For the original Flaks the lenses interchange between Asian and regular fit but with the Flak 2.0 the lenses are different between the Asian and regular fit lenses.
Yes on original Flaks, Asian fit lenses do fit. There's a small difference to the shape and size of the XLJ lens, but nothing major. I think they are cut a little bit higher on the bottom edge. Others are correct here that Flak 2.0 Asian fit lenses are not interchangeable with non-Asian fit Flak 2.0 frames.