All major CAD systems use mature geometry kernels like Parasolid [2]. Parasolid was developed for 40 years and is still in active development. This is the piece of code that enables CAD systems to do things like computing an intersection of a G3 smooth fillet with embossed text, handling all corner cases.
FreeCAD runs on OpenCASCADE [3], which is both less sophisticated today and is slower to gain new features than Parasolid, being seemingly maintained by one person [4]. FreeCAD's geometry is hard limited by what OpenCASCADE can do.
This is the main difference from Blender. Blender ultimately operates on vertices, which doesn't require nearly the same level of inherent complexity. Blender isn't bottlenecked in what it can do like FreeCAD is.
[1]: https://en.wikipedia.org/wiki/Geometric_modeling_kernel
[2]: https://en.wikipedia.org/wiki/Parasolid
[3]: https://en.wikipedia.org/wiki/Open_Cascade_Technology
[4]: https://github.com/Open-Cascade-SAS/OCCT/commits/master/