Posted by Schorsch on Jul 28, 2015; 5:36am
URL: https://forum.jogamp.org/Manually-set-normal-vectors-are-ignored-for-backface-culling-tp4034976p4034982.html

Ah, okay. I forgot about lighting. Okay, then I can see the purpose of setting normals manually. Thanks for the clarification.
By the way, I don't find Java3D frustrating at all. I actually do like the idea behind the scenegraph. It's just that I have all those noob questions. ;-)