That's not the black matter I'm talking about. The one I'm talking about is the one which comes prior to an attack. Both Luffy and Big Mom were emanating the black matter before they attacked.
Also a point to note, Luffy could be using COA there without using hardening but that's not relevant to my point
Also a point to note, Luffy could be using COA there without using hardening but that's not relevant to my point