Yeah, calling a guy a "wizard with a seam" is perfect. I used to think a seam was just a cut you had to hide, but seeing a real pro work changed that. The way they get the pile to lay just right so it disappears is actual skill.
Ever read that old book about the history of carpet making? It talked about how a perfect seam was the mark of a true craftsperson, not just an installer. That idea totally lines up with what @michael_jenkins39 said about it being a real skill. It's not just cutting, it's knowing how the fibers will settle over time. 50,000 yards means that person has seen every kind of carpet and problem there is.