The new method geodesicEllipse() of GeometryEngine allow us to create geodesic ellipses... but API Reference documentation is wrong about Major Axis Directionhere : - it's in Degrees, O is East, but it's measured counter-clockwised !! (like with ArcObjects).
Second thought is that it would be nice to have another reference system for the direction : like azimuth, in degrees, O is North (true North) and it's measured clockwise.