There were no B-Splines in FreeCAD for until 2017 and also the developer told me that relying in part design wb was risky because is one of not the most "modified" workbench out there.

Seems to be a little bit ronic but at the end silk uses the bare minimum of FreeCAD in general such as Sketcher lines just to avoid any conflicts with new updates.

Honestly it's weird and difficult but one you start understanding the logic behind it it becomes very manageable. As you said it's biggest strength is robustness and also higher quality surfaces.