He answers that question in the git hub read me:

"While FreeCAD technically does everything I need, the way it's implemented isn't quite to my liking. My biggest pain points with it are the modal sketcher that only works in 2D, no constraints in 3D for extrusions and the perils of referencing things in the design.

Solvespace on the other hand gets the workflow part right, but falls short by not importing STEP and the geometry kernel not supporting chamfers and fillets."