I’m not rationalizing it at all, I’m just saying what I’ve experienced. And it’s anecdotal experience, so it’s not conclusive. But I’ve noticed it with at least three different chips - all RHCs with a lighter base color and a darker colored edge spot. Shuffle shuffle shuffle, all of a sudden the base color is all dirty with transfer from the spot color.
Not sure why you mention the inlays; maybe we’re talking about two different things. I’ve seen inlays get messed up from casino rack checks, but I’ve never noticed any inlay pick up color transfer from normal playing/shuffling.
Like I said, I’ve never noticed significant color transfer with leaded chips. Maybe I just haven’t had leaded chips with the right colors. And though I believe unleaded is more susceptible than leaded, I don’t know why. Just different clay formulations behaving differently is my guess.