I think this is true in some schools, and not in others.
At my last dojo (Shorin-ryu), this is definitely true. If you cram in as many hours as you could there, you test every three months. From ikkyu to shodan, the hours required takes six months to cram, unless you're willing to shell out some cash for private lessons. And on top of the brutal eight hour test, it's 500 pushups, 500 situps, and 1000 kicks (and that's in addition to the pushups, situps, and kicks you're already doing throughout the test). Nidan and above don't have the 500/500/1000, but whenever a lower ranking person than them has to do pushups for messing up a kata or technique, they have to get down and do pushups with them.
Well the way I see it is that if you're going to have those requirements to get from ikkyu to shodan then to get from nikyu to ikkyu it should be a seven hour test where you have to do 400 pushups, 400 situps, and 900 kicks (in addition to the pushups, situps, and kicks you're already doing throughout the test,). That is just my take on it and just my opinion but it makes sense not to have the shodan test to be out of proportion in terms of difficulty when compared to the ikkyu test. If you're going to have a hard shodan test then the ikkyu test should also be hard, hard enough that the shodan test isn't harder to an extent where it's out of proportion with the difficulty and with the time it takes to get from ikkyu to shodan vs the time it takes to get from nikyu to ikkyu.
Im also of the position the nidan test would be harder than the shodan test where you're required to do more pushups, situps, kicks, ect. then what is required for the shodan test simply because nidan is a higher rank thus it would make sense that it would have harder requirements.
As I mentioned in another thread, this apparently has to do with being under the Frank Hargrove lineage. Also, apparently, this wasn't the way that Shugoro Nazakato trained his students in Okinawa from what I hear.
Frank Hargrove I believe was born in the USA so as I said, I believe they do things differently in terms of rank advancement to shodan than what they do in Japan.
At the Shotokan dojo where I am now, I have not yet seen anyone test for shodan. We only have one ikkyu, and he's not testing for another nine months (there's a one year wait). I'm not really betting money that what happens during the test is much different than the test from nikyu to ikkyu, least of all as different as it was at my last dojo.
So there is a one year time requirement in which you have to be at ikkyu before you're eligible for shodan, I can understand minimum time requirements within reason but what Im against is having a student wait indefinitely just because an instructor wants a student to be patient.
I will say that I'm not buying that black belt is seen as "just another belt" that merely comes after brown. Your rank goes from kyu to dan. That's a much clearer distinction between ikkyu and shodan than between any other two ranks. Think about this:
Hirokazu Kanazawa even has a book called "Black Belt Karate."
Theodore Roosevelt was a brown belt in judo. Why did he never make black belt? Because, at the time, non-Japanese could not be promoted to black belt.
So there's clearly a significance to the black belt among the Japanese.
Well Im talking about contemporary Japan. If we're talking about Theodore Roosevelt having a brown belt in judo that was over a hundred years ago so there's been some changes since then, not the least being that you can now get a black belt in judo without being Japanese. I've seen other changes too, I know a case of a girl from Japan who got a black belt at the age of seven and from the videos I've seen, she's got really good katas but she would not be a black belt at my dojo, the first dojo I started seriously training at, because to be eligible for a black belt there you had to be able to take a hit like a full grown adult. And no you would not just stand there while somebody hit you full force, you would hold a pad that somebody would hit.
I would also like to point out, and you no doubt already know this, that just because you're wearing a black belt doesn't mean you're of the highest rank as there's 2nd degree, 3rd degree, 4th degree, ect. and that black isn't even the highest color. There are styles with higher colors such as in Gracie Jiu Jitsu the very highest belt is the red belt although you have to be a pioneer of the system to be eligible for it.