Mustafa,
It is more about roll response.
The upwind wing is generally in clean air while the downwind wing is never so lucky. Reduced flap is an attempt to moderate the tendency of the upwind wing to generate substantially more lift (more curvature, slight increase in lift curve slope, delayed separation, etc) than its less fortunate partner - the roll away from the wind can upset your otherwise well executed zero-drift touchdown and smoothly controlled roll-out. You can't change the theoretical wing loading but you can influence the symptoms.
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