Well...
I would have to say you'd have to kill ne before I'd hang out with some CO who only does things with numbers, clubs and mace. They don't really use hand to hand in the prisons I was in.
My friend did time in Rikers and other NYC prisons for carrying close to a kg of cocaine. He has not heard anything like that.
Maybe it really is only taught to blacks as he is hispanic and 90% of my other friends are hispanic. The other 10% that included blacks were more people I knew from people I hung out with.
Oh well,,, not imprtant either way. It's your mind that counts. Any decent set of techniques will work. There is nothing special about that system, only the mind set of the people using it.
We're not gods. Not only are our powers limited, we are sometimes forced to become the devil himself.