It is most likely using a Lora - it’s like an add on for stable diffusion that forces a specific style. You can find them ready-made for all sorts of styles - i

It is most likely using a Lora - it’s like an add on for stable diffusion that forces a specific style. You can find them ready-made for all sorts of styles - including black and white line art. Or you can also train your own using a few examples of a style you want to use.