well, now we've strayed......
I'm sure that folks in other organizations would say the same thing. That there is a syllabus and one person/one group that conduct exams, etc.... Be that as it may, there are still posts asking about "how can so and so be at X rank, when their test wasn't very good"? (I believe there was one recently)
Maybe, given a small organization the variation is so small as it can safely be ignored for instruction purposes ---- in the situation that John mentioned. But I believe the larger the organization, the larger the problem, and certainly across organizations the differences are pretty significant (not to mention countries). I admit that this can be worked around, the Aiki Expo no doubt showed this, but then again, I suspect most people started to work slowly and politely until they got an idea of their partner's abilities, regardless of the color of belt they were wearing.