Understanding the IS OF TYPE comparison operator

The Oracle IS OF TYPE comparison operator (IS NULL) allows for the type of an object to be examined. The following example demonstrates its use:

Select Case When Then End MDSYS.ST_Point.FROM_WKT('POINT(6012578.005 2116495.361)',
                                    2872) is of type (MDSYS.ST_Point)
            then 'POINT' 
            Else 'GEOMETRY' 
        end as ofTypePoint,
        case when MDSYS.ST_Point.FROM_WKT('POINT(6012578.005 2116495.361)',
                                    2872) is of type (MDSYS.ST_Geometry) 
             then 'GEOM' 
             Else 'Something Else' 
        end as ofTypeGeom,
        case when MDSYS.ST_Point.FROM_WKT('POINT(6012578.005 2116495.361)',
                                    2872) is of type (ONLY MDSYS.ST_Geometry) 
             then 'GEOM' 
             Else 'Something Else' 
        end as ofTypeOnlyGeom
  From dual;

-- Results
--
OFTYPEPOINT OFTYPEGEOM     OFTYPEONLYGEOM
----------- -------------- --------------
POINT       GEOM           Something Else

The first two results are perfectly correct as an ST_POINT type is both an ST_POINT and an ST_GEOMETRY. The use of the ONLY prefix reports that ST_POINT is not just an ST_GEOMETRY type if IS OF TYPE reports that the result of ST_POINT.FROM_WKT is an ST_POINT.