Yes.
PNG is not used as that is about texture, not color, which Studio doesn’t care about. The .mtl file format is very simple, just a material name and color (and potential texture image name). Then that name gets used inside the .obj file in usemtl commands, alongside all the coordinates. It’s all plain text.
Sorry, I don’t know why this particular import isn’t working. Maybe you could post some files for others to test (anything with this issue, eg. from Hunyuan, not necessarily what you want to print).
-Max