It is my understanding that if the root area has a fairly sharp leading edge and it transitions the outboard leading edges which have a very blunt radius it will be similar to introducing washout. I believe the 'Aquila' sailplane used this principal. The wings were built with no washout. However the wingtips were swept 'up' on that design. So the combination of blunt leading edges near the tips and the upswept wing tips may both be needed to achieve the flight characteristics desired.