enterprise geodatabase - Get ArcMap to recognize ST_POINT (SDE.ST_GEOMETRY)

I have a sde.st_geometry line feature class called ROADS. I've created a view using a st_geometry function called st_startpoint which returns an st_point column. st_point is a subclass of st_geometry; st_geometry is the superclass.

SELECT OBJECTID, SDE.ST_STARTPOINT(SHAPE) AS START_POINT FROM ENG.ROAD

Unfortunately, there is a known Oracle bug that is preventing me from using my view (which includes the st_point subclass column): Bug: Unable to define a query layer in ArcGIS where the data source uses an st_geometry subtype in Oracle.

The bug description states:

...the binding used in Oracle to fetch the geometry binds an st_geometry type. Because the attribute or values returned from the attribute do not map to st_geometry, the Oracle internal error is encountered. By definition, a type binding should support its subtype definitions. This limitation is currently a bug within Oracle's server.

The workaround, if you can call it that, is:

Convert the geometry attribute field from the subtype (for example, st_point) to the supertype st_geometry.

However, it doesn't say how to do the conversion; I don't know how to convert from a user-defined type subclass to a user-defined type superclass. I've thoroughly searched the st_geometry functions, and I don't believe there is a function that will do this. Possibly because, in theory, this scenario shouldn't exist. I ought to be able to add an st_point column to ArcMap, because it is st_geometry (it is already a class member).

In fact, I am able to insert an ST_POINT into an ST_GEOMETRY superclass column in a table:

CREATE TABLE point_test (pt1 sde.st_geometry);
INSERT INTO point_test VALUES (
 sde.st_point (10.01, 20.03, 4326)
);

But, as I said, I'm not able to use the previously mentioned view in ArcMap, due to the bug.

What I've tried:

I took a blind shot in the dark, and tried cast:

CAST(SDE.ST_STARTPOINT(SHAPE) AS SDE.ST_GEOMETRY) AS GEOM

But it threw an error:

ORA-22907: invalid CAST to a type that is not a nested table or VARRAY (#22907)

The Question:

How can I get ArcMap to recognize an ST_POINT subclass column? Do I need to convert the subclass to a superclass as a workaround to the bug?

Unfortunately, I don't have access to the Oracle bug documentation (Metalink Note:49375.1).