You see, in the original screenplay for Bladerunner, Harrison Ford's character was going to be closer to Philip K. Dick's vision; old seersucker suit with a tweed overcoat instead of that untradly leather coat And his gun AND dog would be trad.
Stretch wool is a created through a weaving process which allows more flexibility in the fibers. Its still 100% wool, it just has slightly more stretch. Were not talking about spandex here, but if you were to pull on a swatch, you would notice it has a little more give. This makes for a more comfortable suit, and improved resistance to creasing.