That I find disturbing just thinking about. Shame on you for bring it up here.

Back to the OP's question. It is my opinion that the measurements in cm are not true as stated by others but used for suggesting a size. Some manufacturers use XS, S, SM, M etc... describing a frame size. However, many buyers are leery of that and want to see a # that associates the bike size with something they already can equate to. Remember when we were young and got our little league team baseball caps in the spring and they had sizes in them? Now-a-days the fitted hats are S, M, Lg, XL and not something like 6 ¾ or 7 ¼.