I'm still not sure what Groboto purpose was.

Please correct me, but it looks like a set of primitives you can combine with weird blending options. Everything done is Groboto looks really ... groboto-ish.
The Modo version was an attempt to extend the primitives set by using SDS custom models. I suppose that using OpenSubdiv (or other sub-d method) allows more robust booleans intersection, but probably not as accurate as groboto 'simple' primitives was.

On the top of that managing how the blending or 'fake' fillet is computed (strips) is complicated to control. Maybe some of this limitations has been removed now, but in early version you could intersect a fillet area with an other boolean operation ... so basically you have to handle a complex bool operation trees + fillet as a whole, very cumbersome once you mix 4 or 5+ shapes.

Also preparing good primitives require a good understanding of sub-d modelling, and the end result is a triangulated poly soup that is worse than what MoI n-gones mesher produce.

Somehow the closest thing to Groboto is probably one of those SDF modeler. Results have also very distinctive look, but maybe not as much as Groboto. Been a grid voxel based tiny details are however very hard to create without using relative high resolution, building 'real' assets with it looks like a chore if you don't produce stylized art. MagicaCSG looks quite ahead in the field. I guess there was a Blender advanced implementation on the way, but I haven't much update about it lately.