if i would have studied geometry / mathematic instead of design i would head for a paper:
“traces of spheres in foggy circumstances”. (but maybe this is more a novel…)
for fillets i always imagine a path of a sphere movement…
and as soon as the radius / curvature of the target surface is (nearly) the same (“foggy”) the trajectory should be more careful, more stable, have more inertia…
same for “pointy” fillets - that should and in one point.
sometimes i think, rhinos problematic fillets are also linked to problems of intersect, offset-Surface and Pull…
this is a nice unsolved issue:
there was another crazy example.
(Edit - i found it:)