Why not option loop not work with polyline entity?

This is the demo of cesiumjs, I add option loop true, but it not work.

var redLine = viewer.entities.add({
    name : 'Red line on terrain',
    polyline : {
        positions : Cesium.Cartesian3.fromDegreesArray([-75, 35,
                                                        -125, 35,
                                                        -100, 35]),
        width : 5,
        material : Cesium.Color.RED,
        clampToGround : true,
        loop: true

The PolylineGraphics object does not take a loop option. See the documentation here:


Although there is an issue open for it to add support:


Feel free to add your thoughts or chime in there.