Zoro is the epitome of critical mass.
I don't know how else this would be read differently.
Ashura is "critical mass" incarnated. How else would Zoro spawn his Ashura unless he is giving it his all?
KOH is literally him pouring all his haki into his swords that ACOC lightning trails are showing even when idle. On top of that the overflowing ACOA smoke like thing.
Heck, I think Black Blades is all about "critical mass".
Yoru is the strongest blade that can contain and unleash the strongest concentrated haki without breaking.