It has three different modes:
• You can simply describe a picture, and it'll automatically generate an image using procedural code.
https://kq-styles.specr.net/#/scene/custom/elk-valley
• You can ask it to paint over an existing image. That's what those examples show, like me creating EGA-style equivalents of various scenes from the original Myst.
https://kq-styles.specr.net/#/scene/myst/r01-c00
• The last way is to give it a rough pencil sketch. It's the mode I use the most since it's very valuable when building an adventure game to position objects in a room.
So instead for each room that needed to be rendered they just saved a series of vector instructions that would re-render it in real time. On slower machines, you could actually see the rooms pop in piece by piece. I wanted to kind of approximate that same aesthetic because it's just super cool!