Can polishing remove oxidation from single-stage paint?

Usually yes, if the oxidation is not too advanced. Single-stage paint has no separate clear coat, so oxidation affects the colored paint itself, and polishing removes the chalky top layer to reveal fresh paint beneath. The pad will pick up paint color as you work, which is normal for single-stage finishes. Apply protection afterward, because freshly polished single-stage paint oxidizes again without it.