I have verified a different behavior between polylines and other entities, when setting globe to false and using a CallbackProperty function. Specifically, when I am setting globe to false, without using a CallbackProperty function in polyline positions property, everything works fine. However, when I am setting globe to false, while using a CallbackProperty function in polyline positions property, Cesium throws a rendering error. Note, that this error does not occur with other entities such as point or rectangle.
Following a previous post, I provide a sandcastle example for verification purposes. As you may see, point and rectangle entities accept a CallbackProperty function when globe is being set to false without any error.
I think that all entities should have had a consistent behavior with respect to the CallbackProperty function when globe is false.