From what I've seen with hardie plank and sheet siding is that they only soak up the moisture when left with an edge sitting in water. The original test samples that I nailed in place have weathered rain and snow quite well, no discernible swelling, splitting or flaking. Of course it was painted on the outside. The materials I left, on purpose, with one edge on the ground were exposed to snow and water. They were not painted, other than the factory prime, so may not be a completely valid test. However, the lower inch to two inches did swell and would separate like a delamination.