>>11814880
cute image but no
the code needed to set the ppumask greyscale bit would take up more space than the whopping four bytes needed to define the background palette, also the greyscale mode doesn't even have a black color
the only way they could actually save any space is with 1bpp graphics, and even then kirby's adventure is literally the largest game on the nes, clearly hal didn't give a shit about saving rom space