I've been noticing a stochastic approach to the construction of the homes in Southern Walk. I see most houses being built with ThermoPly exterior sheathing and some (not many) with OSB which I certainly prefer. Plus, on the interior, I see some wood 2x4's and some stell 2x4's. Anybody know why VM uses one over the other ro why the approach seems random? It was a shock to me that TermoPly was used at all since it seems pretty flimsy (will it last 40 or 50 years like typical OSB or plywood sheathing will?). I can't think of any advantages other than weight and perhaps cost (probably the real driver). Thoughts?