From what I saw in that file and a few others (in USDZ), the metalness is not captured. It's in 0/1_b.jpg , and the file is always pure white. You are only seeing roughness I opened them in Houdini and it translates to a USDPreview material, with those PBR channels connected: basecolor, roughness (decent map), metallic (no data, juste white) and normal map (decent map too)