I’m not sure how many people might have done that, but the overlays the person you’re replying to mentions is not that. The overlays literally just show you what colour each pixel should be and a human must place the pixel. Those are used by tons of legit people. While I have no doubt that there is botting, large communities on Reddit can have millions of people. They only have to convince less than one percent of their most dedicated members to use an overlay and they’ll be able to defend a sizable chunk of the canvas.