in reverse the boost pressure acts on the base of the piston in direct opposite to the spring, so one benefit is it may drop boost quicker, but on the other hand it has more of a chance to leak boost too, in comparison of it acting on the side of the piston,
most dv do work as standard in the reverse position, i never understood why VAG fitted it the way they did, all i could think was due to the annoying little chirp it does in reverse,