Death is about killing.
The dead are about the influence of those who exist in a new form of nature, including those who are the corpses of dust and the breaths of wind.
True Resurrection and Clone are examples of creating a new body. For example, if the original body exists but is irretrievable, then there would be two bodies (thus two ki lifeforce aura that cling to each body), but the disembodied mind (being the consciousness and self of the soul) unites with only one of them. There is no actual need to destroy the original body.
To remove a disease by pulling it out as ooze, or simply sweating it out or via urine or feces, is fine. Maybe for the sake of the story, yuckier imagery is more visceral and fun.
Healing damage such as a missing limb has nothing to do with death or destruction.
Except when medicine doesnt work that way, such as by creating prosthetic limb or supplying a missing hormone, nutrient, or other chemical agent, or by supplying "good" bacteria for the healthy ecosystem of the gut.
Killing bacteria and gaining assistance from undead souls ... are dissimilar concepts.
Neither are carnivores who eat meat the same thing as undead. Nor are Fighters who kill in combat the same thing as undead.
Necromancy is more specifically about dangerous magic, including undead, fiend, and the "Necronomicon".