Vector displacement map - settings to bake VDMs from Zbrush

Goal:
Bake Vector Displacement in Zbrush Render in Scenekit/Metal
Process:

Im using this Zbrush diagnostic file, to know proper settings for baking:
http://docs.pixologic.com/user-guide/3d-modeling/exporting-your-model/vector-displacement-maps/
Result:

When rendered in Scenekit, I found no “perfect sphere” and you can see on images attached.

Does anyone know correct settings for VDM in Scenekit?