In the Pixyz example, the material name looks just like the surface color encoded in a hex way ... I doubt it was the original CAD material name.

Beside Dom did a Moi parser you can run inside Houdini :
https://www.youtube.com/watch?v=DE5ygN9ZBFA

It won't help to keep the original CAD material assignment, if nor IGS or STP can care them, the only way would be .3dm ?