Ryuma sword was black and the guy forged it himself and the sword wasn’t part of the 12 supreme grade swords (stupid decision from Oda btw)
Because black blades are in a league of their own, why have we got statements saying black blades are the most elite
Why is shusui valued as a national treasure, if it wasn't a black blade it wouldn't be the mark of a sword god.
Shusui is more elite than any supreme grade blade (that aren't black obviously). That's why it doesn't matter what the initial make of it was. Because a swordsman can elevate their blade to elite status with their own ability, no matter who made it or where it came from.