I have occasionaly come across plain beige twist pile woven carpets that can shrink dramatically. These have been around since before BW days. This particular type seems to have a synthetic rather than jute construction with cotton stringers running through. Obviously its the cotton that soaks up the moisture that will freely run down all the synthetics, thus badly shrinking. As for recognition, patterned BW are obvious, but all wovens should be treated with suspicion. Natural Backed wovens, the tighter the backing construction the better, beware the lesser dense ones.
Dave.