The comment: “If we don’t have a higher grade we aren’t taught the stuff that is taught to the higher grades”.
In practical terms, there actually is very little of the upper stuff in seitei gata instruction, it’s all detail for all ranks for us in the west. Mostly because the majority of our numbers are at 5dan or below, which is the end of the detail stuff and beginning of the riai (which is really and truly just the fundamental stuff). Detail can be taught in riai and riai can be learned from the details so again the easiest is to stick with the details. It’s a whole that should not be divided, but unfortunately often is.
In Canada we become instructors too early, and we upper ranks rarely teach classes of 4 dan or above (because they are teaching in their own classes, assisting in ours, or just plain ignored during class since they are just fine at the 2dan stuff we’re teaching), we let them learn the riai on their own.
Again, this system is mainly continued because it’s easy. It is difficult for any instructor to hear something new, especially if it contradicts what they have been teaching or thought they knew. An instructor must first and foremost believe they are correct before they can correct others. Wishy-washy doesn’t cut it with beginners, their BS antennae are always on high so an instructor must have an ego and be able to insist they are right. Being “wrong” is not an easy thing for a 4dan who has students, but it is also not easy for the 7dans to hear things either. We all develop the wax of authority which we ought to clean out of our ears once in a while so that maybe we can hear something new.
Having a higher grade so that you can move next door to the other class becomes a goal after a while. I get all sorts of requests to move to the “next level” in seminars, and if I can get away with it I let them go. That’s the easiest way to show students that either they are not missing anything secret or special (those two are not the same by the way) or that they are not ready for the next level.
Why do we split seminars into levels? Because we actually are trying to teach more advanced stuff to the advanced students. What is more advanced? Well beginners learn footwork and big shapes, intermediates learn details like where to stop cutting when you cut someone on the face and stop at the chin. (In other words we are teaching people how far from the floor their own chin is) and for the highest levels, we are often teaching them how high from the floor their chin is so that they can teach their own students how high chins are from floors. In other words, you step next door to the next group and you might be getting the same information at a faster pace, but the real difference is that you’re getting a different instructor (if it’s a seminar with multiple groups).
Many years ago I noticed that our top instructor at one of our yearly seminars had abandoned us top rank folk and moved on down the line to the beginner group. He really liked teaching beginners, probably because teaching us upper ranks was like hitting his head on a wall to get to the other side. I spent a lot of years trying to figure out how to get from my “top group” class down into the beginner class. The grass is always greener of course.