In the US we have been using that for markings though, James, with little attention to opaqueness of white or red. For example, how often have we seen SS mean Hinomaru, or SSS mean Mosura? Yet both displayed poor white coloration?
Somehow in the USA, S, SS, SSS has been bastardized to become tied to pattern instead of opaqueness.
Originally, S was separate from markings. You could have a grade A Hinomaru for instance, yet when was the last time you saw that advertised? Heck, look at grading charts on the web and many of those are even confused on the system.
...I don't know anymore...maybe this has been adapted to the new way. A specific grade equals a pattern. I remember when Silane came up with SSSS for his almost all white shrimp.
I miss the opaque grading system though...