CESIUM_primitive_outline mess up outline when gltf primitive share the same POSITION and indices

Hi I am trying out the CESIUM_primitive_outline on my 3d model. I realised when my primitives share the same accessors/bufferview for its position, normal and indices the extension does not work as shown in the image below. This is essentially a geometry array that has the same geometry but different placements. Am I not suppose to use the extension in this case? Or is this a bug of the extension? Thanks.

outline.glb (4.9 KB)