is there any documentation of how pc-98 artists made their dithering? some of these gradients seem too complex to have been done pixel-by-pixel

this place has no dms so shoot a message at mogggg on discord, please don't be weird
if u want to see only my drawings:
is there any documentation of how pc-98 artists made their dithering? some of these gradients seem too complex to have been done pixel-by-pixel