Gradient Fills are hard-coded into ArchiCAD, so I can't see any way to trick Attribute Manager to create a copy of the material with a new internal ID #. So AFAICS it is impossible to assign one to a material.
Furthermore the gradient fill has it's fill orientation and distortion locked out, so there's no way to magic wand an area and set the orientation on the fly.
[The
geometry
of elements are never transferred with a parameter transfer, so it would never orientate itself automatically anyway].
At the very least you are able to rotate the fill orientation once it has been placed. I guess that's something...
Cheers,
Link.