That's an idea of what grades are and what they're for. It's not the idea. I would call this an ideal, often fallen short of, and often misguided.
In practice, grades are used in all sorts of ways for all sort of reasons. Many times, they are used for no good reason.
The idea that tests are impartial accreditation is abstract. It rarely plays in reality. There's a place for GMEDs, bar exams, TOEFLS and whatnot... but it's limited.
>It is extremely important to intellectual freedom that the time and place where some knowledge or skills were attained is considered immaterial.
> The idea of someone not getting accreditation in a course because they already knew the material beforehand and so didn't learn anything is completely wrongheaded and abhorrent
It's abhorrent only within the accreditation framework of ideals. This just isn't reality. That objectivity ideal for education is always betrayed because it doesn't work.
People don't value exam results, in their own right, because they're not that valuable in their own right. A course's job irl is to educate, not accredit.