Most of our art drawings including the star and moon above were hand drawn, before scanning the drawing, and editing the picture in an editing software so that it doesn't have any background disturbances.
There is a couple of cgs I had drawn in person including this one for a plan, I had painted it and scanned it in, then I used an editing software to make it look way better, including without disturbances in the background.
I have no doubt that the sketches you've shown aren't ai, but the pictures in the preview are ai altered. Many editing software uses ai. They make you choose a theme and they'll use ai to alter the image according to what you chose. Just informing you.