The black paint inside the lens is intended to reduce stray light in some conditions. If white paint was used instead black you would notice an increase of stray light (non image forming light). At the end the dots from schneideritis have an small total surface, so no increase in stray light can be noticed. If a large share of the inner surface was peeled off, sun was not in the framming but still bathing the glass, and no lens hood was used... then some increase of stray light would be noticed.
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