I've measured tube wall thicknesses that were close to 10% thicker than listed. Spec charts are not always what goes on the production floor and tube decals don't always match up with the actual tubes used. Steerers and stays are often not the same grade as the rest of the frame and are a cost savings "location". Cast lugs and other fittings often weigh more than the stamped and folded examples. And then there's how the frame was weighed, not as in which scales were used but what was included or not. Did the frame still have the fixed cup and headset parts on it??? (Back in the 1970s as I became aware of fancy Itl. bikes I noted the often sub 20lb weight claims. Well, for a 19" framed bike with no tires that's about right. Andy