You gave a nicely worded explanation ,I couldn't have done it with googleI can see what he means. It's the topology of the interveinal region that's causing a light side and a dark side to the curvature of the surface. In some photo's, due to the relative angles, it looks like a flat surface with pale striping to the leaves. A classic mag deficiency symptom. But I think, from the other photos, it's just an optical illusion.
Actually you may be right optical illusion