I have a suit made from Smith Botany 3912, same plain weave as 3913 (not hopsack) but one shade lighter, and I consider it to be very much a smooth business worsted. The navy hopsack from the Steadfast line, which I have in a blazer, is significantly more rustic and textured.
Are you saying that 3913 is not a hopsack, but a plain weave? What's the number of your Steadfast hopsack? Thanks.