cesium no supports loading external "binary buffer" of glb in b3dm?

[hanaimin]

In the 3d-tiles b3dm specification. there is a describtion:
Instanced 3D Model embeds glTF 2.0 containing model geometry and texture information.
The glTF asset to be instanced is stored after the Feature Table and Batch Table. It may embed all of its geometry, texture, and animations, or it may refer to external sources for some or all of these data.

But , in cesium, when the b3dm loaded, the external "buffer binary" can not be requested. is it a bug or missing function?
"buffers": [
{
"byteLength": 1113924,
"uri": "0.0.bin"
}
],
tileset.zip

[hanaimin]

function parseGlbVersion2(glb, header) { var length = header[2]; var byteOffset = 12; var gltf; var binaryBuffer; while (byteOffset < length) { var chunkHeader = readHeader(glb, byteOffset, 2); var chunkLength = chunkHeader[0]; var chunkType = chunkHeader[1]; byteOffset += 8; **var chunkBuffer = glb.subarray(byteOffset, byteOffset + chunkLength);** byteOffset += chunkLength; // Load JSON chunk if (chunkType === 0x4E4F534A) { var jsonString = getStringFromTypedArray(chunkBuffer); gltf = JSON.parse(jsonString); addPipelineExtras(gltf); } // Load Binary chunk else if (chunkType === 0x004E4942) { binaryBuffer = chunkBuffer; } } if (defined(gltf) && defined(binaryBuffer)) { var buffers = gltf.buffers; if (defined(buffers) && buffers.length > 0) { var buffer = buffers[0]; **buffer.extras._pipeline.source = binaryBuffer;** } } return gltf; }

it seems as the parseGlb.js parseGlbVersion2 function no supporting to load external .bin file