I would think it is just either bad phrasing or meant to be misleading to the eye so your brain sees and thinks "mint".
I would say if its a 1-10 or 1-100 scale, a 9 is a 9/10 or a 90/100 - its the same thing.
A c1 or 10 of mint would be a beater that a dog ate and crapped out and then was a beater again I think.
Crafty wording to lull in the masses to want to buy it most likely or simply just a bad choice of words.
I like the collectible card grading system (honor system, not professional)...
Mint/Pack Fresh
Near Mint
Excellent
Good/Played
Fair
Heavily Played/Shite
All have a range of + to -.
It leaves a bunch of guess work out but yet leave some honest subjective thoughts.
Mint is perfect, near mint is damn close... excellent is very subjective but very very close to near mint.
Good is where it gets a bit into a grey area, but mostly not bad at all.
Fair, well, now we are getting close to heavy wear and close to a beater.
Heavily Played/Shit - do I need to explain?
It is one reason I take high quality pictures so I don't have to say it is XXXX condition. I am not AFA, so I won't speculate a real grade. I just say its great, good, excellent, etc.
Anyway... I know this didn't answer or help much, just my thoughts on the whole user based grading system.
It will always be subjective outside AFA grades and even still we see so many people disagreeing on the grades AFA puts out there sometimes.
cheers!