@Harlock I think you missed the obvious causality loop created by the mismatched timelines between Earth and this planet. People who arrived hundreds of years before the MC obviously lived in societies that were similar in technological development to the MC so they are probably from a similar timeframe as the MC himself. The spacial hole that the MC's spirit made when being drawn to the new world has temporarily fixed the timelines between the two worlds but when that hole eventually closes, the timeline on the fantasy planet seems to jump around a lot but the timeline on Earth seems somewhat fixed (or at least not as extreme).
I'm not sure if that fully explains the choice of the illustrator but it should be helpful.
I'm not sure if that fully explains the choice of the illustrator but it should be helpful.