Found it! This is what's making me leery of going with the lamb although I love the way it drapes. It would be not necessarily rough but definitely fairly regular wear, if that makes a difference?
It is pretty noticeable in that picture; I'd be interested in seeing a calf with that kind of wear in the arm just for comparison, but I think this effect is unavoidable in any jacket that has slim fitting arms over time. My denim jacket (not TOJ just in general) has a similar bump around the elbow, and I really love the way that lambskin jacket has creased.