Physical Groups and Periodic Implementations not Persistent
When a physical group or a periodic element is defined, an OpenCASCADE operation will remove them.
A physical line that is intersected with a boolean operation will disappear.
In the case of a cube with a periodic surface, this means that it is not possible to enforce periodicity in the mesh. In the tested scenario, the periodic cube has a single sphere intersecting the surface, therefore, it is replicated on both sides of the cube. Even if the user uses the GUI to find the new surface ID's and manually re-implements a periodic surface for the sliced surfaces, the mesh is not periodic.