By default, curve geometries are not fetched from services that support curves, meaning that densified versions of any curve geometries are fetched from the service. Additionally, by default, Runtime indicates that is it not a true-curve-capable client when sending updates to services that support curves. Use ArcGISRuntimeEnvironment::serviceCurveGeometryMode to change this default behavior.
For details of curve support in services, see ArcGIS REST API documentation.
The ServiceCurveGeometryMode can be one of: