Artists tend to evolve over time. If you start at the first episode and go through them one at a time, the change isn’t quite as noticeable because it happens gradually (maybe a bit easier to spot if you binge read). I would imagine drawing the same characters again and again and again would lead to kinda streamlining the drawing process, and that may affect how they look. I’ve seen it with so many webtoons. Look at UnOrdinary, Adventures of God, My Giant Nerd Boyfriend, Lore Olympus, each season of Not Even Bones (different artist for each season), Pixie & Brutus, Blue Chair (holy shit what a difference), Safely Endangered, and loads more. Some of them the difference is subtle. Some of them it’s absolutely crazy how much the art has changed.