Actually, as I think of it, the Macchi designers were attempting to counteract the torque of the propeller and engine which would tend to cause a left-wing heavy condition. Their solution, rather than offsetting the vertical fin like some others did, was to extend the left wing, giving it a little more lift. I don't suppose the designers (this was used on the MC 200 also) thought to change the camber of the left wing for added lift but rather just extended it. In essence, they were simply trying to "pick up" the left wing by adding lift. I'm guessing they used their slide rules to determine if adding wing span caused less drag than offsetting the vertical fin.
As to this model, I've begun painting and will get a photo or two posted soon!