I was also confused about "black pieces are useless" as 2 white queens looking at each other can be replaced with 1 white and 1 black to add moves about eating

I was also confused about "black pieces are useless" as 2 white queens looking at each other can be replaced with 1 white and 1 black to add moves about eating each other - but then I realized it's simply "only 1 side can move"