This is a total guess, but maybe it has to do with the rims lip along the edge of the tire. Most factory wheels seem to have an extra lip along the outer edge of the rim on both sides, where a wheel weight is normally clamped. On most aftermarket rims, this little edge/lip where you would clamp the weight isn't there (instead, stick on weights are used on the inside). I wonder if they have removed that lip/edge from the wheels to make them look more like aftermarket, to have a smooth transition to where the tire begins. Again, thats just a guess.
Does anyone have any closeups of the Sky's rims?