Or create a row of all prim types (cube, cylinder, sphere, prism, torus, ring, tube) lined up at an angle pointing to the sun (so the shadows cast onto the prim behind the one in front).Observed results: Shadow/shading non-uniformity all over the place. A torus' shadow on a sphere isn't even close to being correct. Shadows are too jaggy and not smooth at all.
Reduce light detail to "all local lights" (or lower), and shadows/shading looks more uniform (but lacks many shadows).
LOD level (zooming cam in/out) also seems to affect shadows: closer will cause more shadows that shouldn't be there and turn on/off at, seemingly, random times during zooming. This is with full object detail, too.
Expected results: Correct shadows!