Threshing has nothing to do with the husks. Threshing is the process of separating the kernels from the straw, chaff, leaves, dead grasshoppers, etc., so that only the whole grain remains. Malting barley is a bit more challenging to thresh than wheat, oats, rye, and other cereals, because of the need to preserve the husks. Grain farmers who try to grow malting barley for the first time are often surprised to find that their harvest won’t be acceptable for malting because, in the course of trying to get the grain as clean as possible, they skinned the husks badly enough that the maltsters don’t want it. Properly threshed malting barley is ugly to look at because, to avoid damaging the husks, a bit of the “unmillable material”, which buyers of wheat and other cereals don’t want, is deliberately left with the seed.