That's from Mr. Rion, not Iwasaki or any credible source, and has only been supported with assertions and flimsy stuff like "an old barber told me!" and "every Japanese person does it that way."
Adding to the fact of what I pasted even Iwasaki saysThe bolded part is angle to the face, it and the Japanese original text are not discussing sides. A low angle can be achieved with either side."If you try using a razor at a standing angle, the edge will very quickly start to show signs of
damage, and an edge that should shave 200 faces or more will only shave around ten. So if you
think you'd like to preserve your edges as long as possible, keep the blade as flat as you can when
Hence not using the other side just sticking to one side will make the edge last longer. So shaving the traditional way with a Kamisori is meant to make a Kamisori edge last longer.
I'm not asserting there cannot be a tradition, but it has not yet been expressed from anything approaching a good source.
P.S sorry if the previous post was facetious and I took it seriously.
Last edited by Tierdaen; 08-19-2013 at 06:07 PM.