Good question, and appropriate.

From a practical standpoint, I'd guess that the rings or the lands do not sustain any increased wear beyond the normal amount. The pistons ALWAYS move side-to-side slightly because of the cyclic loading on the piston crown. In the case of piston slap, the pistons are also rocking slightly, but perhaps only a few extra ten-thousandths of an inch. My opinion is that this would mean nothing at the mid and top regions of the piston. And don't forget that the rocking is minimized once the engine reaches operating temperature.

Keep in mind that the dimensions we're discussing are tiny -- on the order of a few wavelengths of light, and much less than the thickness of human hair, even mine.
--
Don Foster (near Cape Cod, MA)