I attached the hip file. There are some overlap points after the boolean operation and the inside (interior) faces still exist. Even the group node fails to detect the unshared edges.

To be honest I don't understand what your issue is. But if you don't want the interior faces you can uncheck "Create Interior Surface" in the Voronoi Fracture SOP.

As for the "Unshared Edges", they are not detected, because there are none. In Houdini an "Unshared Edge" refers to an edge, that is not shared between different primitives or polygons. You can spot holes or corners on open geometry with that option, but not on voronoi shattered pieces. These are closed meshes usually (except you deactivate the option for interior surfaces mentoned above).