[JJ_SO]

Distortions will not vary between samples in any substantial way.
Of course, there'll be slight variations - lenses aren't digital after all - but there'll be no qualitative difference.

Can you quantify the "non-substantial" way? To me the diff between  -1.28%, -1.35% makes 0.07%. I would not call that "substantial". That was my reason to ask for sample variation. Be it that, or variation in measuring method, I still don't believe that distortion is absolutely excluded from any variation. The differences might be very small and neglible, but there's absolutely no reason why this property should not be affected. There are differences in resolution big enough to appear on charts...