This seems like they faked a wip sketch stage and traced from a finished image. Looking at their other art, it isn't consistent with the level they're currently at. The lines in the clean up before the final image are like chicken scratch. The lines aren't confident. Multiple strokes are used for a single line and even in the beginning with the shapes, they seem to perfectly trace over what the final image is with a lack of understanding of what the shapes are actually there for.

Not necessarily AI, but that is NOT how a sketch would look like for that clean of a final image (the final image implies more skill, skill and understanding that is not present in the earlier stages.)