ArcPy: Edit vertex without removing true curves

Bud

I have a multipart polyline FC that has true curves (Oracle 18c SDE.ST_GEOMETRY).

I want to update the coordinates of the vertices in the lines via ArcPy — without losing the true curves:

import arcpy
connection = "Database Connections\my_conn.sde"
feature_class = connection + "\my_owner.my_fc"
spatial_reference = arcpy.Describe(feature_class).spatialReference

with arcpy.da.Editor(connection) as edit_session:
    with arcpy.da.UpdateCursor(feature_class, "SHAPE@") as cursor:
        for row in cursor:
            geometry = row[0].densify("ANGLE", 10000, 0.174533)
            parts = arcpy.Array()
            for part in geometry:
                points = arcpy.Array()
                for point in part:
                    point.M = geometry.measureOnLine(point)
                    points.append(point)
                parts.append(points)
            row[0] = arcpy.Polyline(parts, spatial_reference)
            cursor.updateRow(row)

The script reconstructs and replaces the geometry of the lines. So, unfortunately, it removes the true curves from the shapes.

Before running script:

After running script:

---

Idea:

Could ESRI consider giving us a clean way to edit vertices — without removing the true curves from the SHAPE?
 - I don't want to densify the curves into straight segments...I want to keep the true curves.
 - It would be ideal if there were a clean way to do this; not a workaround like converting to JSON and parsing out the curve info from the JSON text (would be messy/fragile).

For example, a simple method like this would be helpful:

UpdateVertex (shape, partNum, vertexNum, [z, m]) 
#It wouldn't replace the shape or replace the vertex. It would *update* a coordinate in the vertex.
#So the true curves would remain intact.

AlexMarkov

Some geometries in ArcGIS are created like parametric elements (arcs, ellipses).

It should be able to get this information somehow from the properties of arcpy.Geometry, arcpy.Polyline, arcpy.Polygon classes.