As I dunderstand, the two materiels were not
generic but specific...wool and linen. While it might not be completely satisfying to dig into the background and find the reasoning behind what seems to be a ridiculous law, such could offer at least some help. People were of different thinking back then and will be of different thinking tomorrow. Using today's thinking on old practices isn't really being fair, IMO. If it worked for them...just fine with me.