You can essentially teach any horse to use a bit as a "signal bit" It is the way in which you use the bit to communicate with the horse. A spade bit is not a leverage bit, if it were to be it would be very harsh. I have always been taught that the spade it is a bit classification. But within the classification there are many different designs and styles. I think we are essentially saying the same thing. However not all spade bits have a similar mouth piece, not every spade bit has a spoon and braces.