H. G. Muller wrote on Fri, Nov 3, 2017 07:55 PM UTC:
I suspect that the table only lists what is 'insufficient mating material' in the sense of FIDE rules, namely that no mate position exists at all, not even a help-mate, and that this immediately terminates the game as a draw. I cannot imagine that you could force mate with Knight + Vao. (But my EGT generator doesn't do hoppers, so I cannot say that with mathematical certainty.) It is already very hard to drive a bare King in a corner with Bishop + Knight, while the Bishop can attack lots of squares without a screen. Once trapped in the corner of the Vao shade by King and Knight, it would be possible to checkmate the bare King in a corner (say a1) with the Knight on c3, and the Vao on the main diagonal.
I suspect that the table only lists what is 'insufficient mating material' in the sense of FIDE rules, namely that no mate position exists at all, not even a help-mate, and that this immediately terminates the game as a draw. I cannot imagine that you could force mate with Knight + Vao. (But my EGT generator doesn't do hoppers, so I cannot say that with mathematical certainty.) It is already very hard to drive a bare King in a corner with Bishop + Knight, while the Bishop can attack lots of squares without a screen. Once trapped in the corner of the Vao shade by King and Knight, it would be possible to checkmate the bare King in a corner (say a1) with the Knight on c3, and the Vao on the main diagonal.