vtkMapper relative coincident topology factors and units are not shallow-copied
vtkMapper has coincident topology resolution factors/units relative to the static/global factor and unit. Besides that the setters do not call Modified() which I think they should, the vtkMapper::ShallowCopy does not copy the relative factors/units. As a consequence, vtkCompositePolyDataMapper2 will not use any relative factors because vtkCompositeMapperHelper2 calls vtkMapper::ShallowCopy.
As a side note, vtkCompositePolyDataMapper will also not use its relative factors/units because it just creates a vtkPolyDataMapper to do the mapping without calling vtkMapper::ShallowCopy to copy its settings.