Thanks for taking a look. I intentionally put the datum plane to be slightly below the top of the object. (Z=14.9mm; object has 15mm radius.) That allowed me to show the portion sticking above the plane easily in pictures.
Tried this morning. This is definitely it. Both Angular deflection and deflection improve the view. More importantly, knowing it's a view artifactly only, and knowing how to affect it are key. It allows me to ignore it or temporarily change it to keep computation faster.