When I say skins, what I mean is that the Forsworn are wearing ragged pelts that are less sophisticated than the basic fur armor that the lowest bandits use. If we use guards as the standard measure of Nord equipment then Nords make use of chainmail, scalemail, steel, and worked leather with Iron/Steel weapons, whereas the Forsworn are wearing bearly worked pelts with weapons made from sticks, bones, and fucking flint.
I think that it makes the Forsworn look like retards when they are trying to fight a war semi-naked with rock axes and it makes it hard to take them seriously. I think it would have been cool to see the forsworn wear Imperial/Stormcloak/Markarth guard armor that they have dyed, added embellishments, or carved, with the occasional higher-level unit wearing metal Forsworn armor. I think it would really make the Forsworn feel like guerilla fighters, fighting a war of attrition in the mountains rather than smooth-brained weirdos ruing around in loincloths.