Your confusion comes form the old quality gradations. Rest assured that the Coticules from Ardennes are exactly the same rock as what they mined in the old days, with exactly the same variations as the Coticules from yesteryear.
The only change is that they no longer use the old quality gradations.
No all Coticule companies used the same gradation system. There were several and they were as much inspired my "marketing" as by real differences. It's difficult to know what parameters they exactly used. Cosmetic appearance was certainly one of them. People have always been willing to pay more for a paler and more pure looking stone. It's perfectly human to put something in a separate class, if you notice that the demand is higher than the availability and raise the price. That isn't always related to genuine quality claims.
But, they way Coticules were used in the past, the emphasis was more on what we now call "bevel work', hence speed was important.
We know that La Veinette and La Petite Blanche went into the highest quality gradations. I don't think it's a coincidence that these consistently deliver fast Coticules.
On another note, they did not only sold Coticules to barbers. They also sold them to wide array of other craftsmen. It seems to me that they tried to differentiate between those different uses. Not so much because Coticules for woodworkers can't handle razors, but because a woodworker is going to wear his Coticule at a much faster rate. Neither is he shaving his face with his tools, so he might be tempted to buy a cruder hone from another kind that works as well, but costs less. So you make a cheaper category and sell Coticules to woodworker, leather workers etc, at prices they're willing to pay. And you tell the barbers that they need higher grade (read more expensive) ones. After all it's business, and it was run by people who knew how to market a product...
At the end of it all, I'm testing these hones in the Vault, that without doubt represent the full range of what they had to offer in the old days. Take for instance, your La Grosse Jaune. I translate from the book of Charles Gaspard, "L'Industrie de la pierre à rasoir dans la région de Sart-Lierneux" (it can be downloaded from the Heritage section): "La Grosse Jaune delivers a razor hone of inferior quality". Nonetheless, you and I both know that La Grosse Jaune gives a very smooth finish that is fairly easily to attain. What it doesn't provide is speed
In any case: I do believe that you own the full spectrum of Coticule properties. You have from very fast to slow, and when it comes to finishes: vividly brisk to smoothly mellow, not necessarily correlated to the speed of the hones. You can buy a 1000 others, they will all fit within the range you already own. Of that I am very certain. Sure, there are layers currently not being accessed. But Coticules remain Coticules. There is are no magical ones out there, that will outperform all others.
They're like women. I like them all, but I love mine. If you turn that around, you'll end up in serious trouble...