In some cases (eg Polygroup selections on faces and edges), only the TopologyIDs are unique, and the same TopologyID may be paired with an arbitrary TriangleID/EdgeID. FGeometrySelection is currently not aware of this distinction, however it means when (for example) adding to a selection, a new uint64 ID should only be added if the TopologyID is unique, ie the ElementID bit should be ignored. FGeometrySelectionEditor can do this, by enabling TopologyIDFiltering in the various setup/config functions.