ITopologicalOperator6.SimplifyAsFeature simplify the geometry according to the type of the geometry.
If the geometry is multipoint type, the method works just like ITopologicalOperator::Simplify.
If the geometry is a polygon, it works as IPolygon::SimplifyPreserveFromTo.
If the a polyline, it is the same as IPolyline6::SimplifyNonPlanar.
ITopologicalOperator6 does not inherit from other versions of ITopologicalOperator.