I think that in many cases thew seller is simply trying to get some money for a bicycle that they know very little about and are not interested in learning more. If the bike sells, all to the good, if people ask questions, too much trouble to find out. Going back to the OP's question asking about standover height, that somewhat goes the other way. Standover height is a very crude bike frame measurement that often doesn't work out. My 54 cm Look 481 sl has an unusually long top tube, closer to the top tube length found on most 56 cm bikes. For this bike, standover is a useless measure. To be clear, the Look 481 SL has a traditional level top tube