>>50278291It can just happen. The guy also added those numbers which don't actually fit in with a real Japanese leak as they're added for the artbook releases.
Even people that get it right in some images get it wrong in others. This old classic that ended up becoming TemTem stuff is right on the money for the water and fire starters, but the lemur actually is lacking the detailed full back drawing.
Sometimes people just forget to add it, but that wouldn't happen in an official Pokemon piece because they surely have some standards they have to keep to for the concept art.
