No, the MDSYS.ST_Geometry Type is not supported by Oracle enterprise geodatabase. The MDSYS.ST_Geometry Type is an Oracle type that wraps the MDSYS.SDO_Geometry type.
For more information on the MDSYS.ST_Geometry type consult Oracle Spatial documentation.
Note: The MDSYS.ST_Geometry type is not the same type as the SDE.ST_Geometry type. MDSYS.ST_Geometry is a type that is created and maintained by Oracle. The SDE.ST_Geometry type is created and maintained by Esri. In Esri documentation, ST_Geometry refers to the SDE.ST_Geometry type.