Author here. All the common stuff (that is based on 3D CSG without extensions) works fine, and most for 3D construction operators just produce a polyhedron with a simple algorithm (e.g., linear_extrude), so that's fine, too.

But some of the more advanced CGAL based operations for constructing 3D objects will not work in 2D, because they are inherently 3D and complex, e.g. 'hull', 'minkowski'.