Material-mindedness is really a different way of thinking. It is not directly connected to the 'materials' in question; instead, these are the closest approximations or metaphors, and not necessarily consistent between societies.
A noticeable effect of material-mindedness is on magic use, where it is generally limiting. Some material-minded individuals have trouble understanding a whole range of concepts.
The huge majority of people, and magicians, are not material-minded.
It is extraordinarily improbable, and may well be impossible, to think convincingly like another person, even when there is not a gross neurophysiological difference in the way. Thus, any attempt to describe or imagine a material-minded person's thought process can only ever approach an educated guess. (But it's such fun.)
An educated guess follows.
Weft's material-mindedness surrounds cloth and thread. This is not because he's good at working with cloth; rather, he's good at working with cloth because he's found something that thinks like he does. Understanding this distinction is essential to an understanding of material-mindedness in general.
Weft understands things on a very basic level in a way that can be (metaphorically) described as weaves and folds.
He's not brilliant at magic, which (from certain people's viewpoint) is a pity, because his methods would otherwise make a fascinating study.