[Graham Boak]

I agree that it is normal to expect washout near the tip, because that is the part of the wing that will twist most and hence otherwise stall first (not the wing overall, just at the tip). This is unsatisfactory because any asymmetry will result in severe un-demanded roll. Building in the washout inboard may end up with the same result overall, but does seem to be aerodynamically inefficient. If it is structurally more efficient in this case, then it can be regarded as an example of the trade-off between different factors in every design.