I thought I saw earlier in the thread that you do get them, but they don't show in the workbench till you come out of crafting then go back in
Yes, this is right, I just done an experiment with it. After I done a modification to a gun and exit the modification window, when I went back to check the workbench inventory it didn't show but after I opened and closed the Settlement visible area, forgot what it is actually called, but its where you have all the buildings, wall etc etc.. then it showed 2 added cloth to the inventory. So hopefully that means it works for all junk items that gives more then one item.