I do think that 28" and 29" wheels use rims that are always the same diameter as 700c wheels. 27" wheels have a larger diameter rim than 28" or 29" wheels; this is silly.
i think that is the size standard for tubulars/singles. They are basically the same as 700c but due to them being singles there is another sizing system. Im pretty sure that is what it is. Just something else to confuse us.