in Jeff Wagner's Houdini VOPs webinar he shows how to inherit an attribute from SOP to MAT. But I am doing the opposite, from MAT to SOP, and so far no result.

Below is my scene. I use a Ramps pattern in MAT context and export it as an attribute. Then in SOP I import it with an Attribute VOP to use this attribute for PolyExtrude's Distance Scale feature. My attribute value in SOP shows only 0.

So what is the proper way to do that?