I’ve discussed this before about somebody who posted on a martial arts Internet forum, not this one, who said his instructor required patience to get a black belt and for rank advancement in general. He didn’t really get into detail about the system that his instructor used for rank advancement except to say that the instructor tells the student when they will test because patience was a requirement. So for instance lets say there’s a brown belt student at his dojo and the next time the student gets promoted it will be to that of first degree black belt. Even if the student is skilled enough to pass the test the instructor might not tell the student they can test because he wants the student to be patient. So when I posted about this before some people said that this was a good idea but I don’t entirely agree, I think if somebody is skilled enough they should be allowed to promote because, number one, time is precious, and number two, if a student has skill that means they’ve got patience simply because it takes patience to develop skill, that’s just my position on it.
I can't talk of general MAs, but in Shotokan karate, for example - and I suspect most of his derivatives - this is exactly the point. The whole knowledge of the "skill" in the sense of combat skill is left very superficial, on purpose. Funakoshi writes that himself - in the past one went for depth, he was going for broadness and fast pace of progression. Because he had other objectives.
You can compare getting a black belt with getting a driving license: you know how to move a car from A to B (hopefully) without doing any damage, but
you aren't necessarily a racing driver; indeed, most people having a driving license aren't and never will be.
Karate-do is a -do: a way to betterment, according to a specific definition of "better". Aside of fitness and health, the qualities it is designed to instill are grit, patience, respect for the elders, courtesy, obedience to the authority and so on. These are the ones required to advance in the game, as much (actually: much more) than any real combat or technical skill.
It actually works well, for the most part. Patience is a skill, and it makes sense to train it - either when you wait in seiza for your sensei to give the ok to move, or when you wait for him to decide on your grading. You are training the -do.
On the other hand: the kind of skill I suspect you have in mind does not care about belts at all. If you're a racing driver, you know how to drive from A to be faster and safer than most, whether you have a driving license or not. Actually, loads of teenage racing drivers can't drive yet on public roads but have far more control of their vehicle than most grown ups. That doesn't make them grown up. It's just a different skill.
For that kind of skill, nobody can promote you because you promote yourself by surviving every encounter where you have to use it. There were no belts in karate before it became an hobby (or a job), because the whole idea was meaningless.
So there's no contradiction. You may physically ready but not yet ready with your character; or the opposite. You will be given your license only when you're ready on both.
Obviously none of this is fun if what you care for is the combat skill. But then again, in that case, why caring about the belt?