>>536049341
Comically low quality image, but monsters are unable to use magic in the Light World. This and Noelle's dialogue about spells too.
Furthermore, Queen's discussion about every Lightner being able to make fountains through Determination, despite almost every Lightner being a monster besides Kris. Or darkness as a force, which wasn't a thing in Undertale. We never see a SOUL do the shiny thing in Undertale either, but that's a thing that happens in Deltarune. Kris ripping the SOUL out, which we haven't seen before either... Many small differences that don't quite add up under the idea both of these worlds are meant to share the same basic rules between eachother.
Monster funerals are a little more complicated than Undertale's too, having the item buried and whatnot, but you could chalk that up to religion (or the kid who wrote the book being stupid.)