Referring back to somebody's comments about "true names," I think I understand where they were coming from better, now. Or, maybe I've come up with a different take based on their notion. Either way, thought I'd share the thought:

"Billy the Halfling" and "Billy the Zombie" are still both "Billy the creature," Billy's just changed type (from humanoid to undead) and gotten a template. Now, the soul isn't there for Billy the Zombie - at least, not nearly enough of it to matter for most purposes - but Billy the Zombie is still Billy, and Billy is not dead: he's undead. Raise dead et al only work to bring the dead back to life. To turn the dead into a creature. Billy the Zombie is already a creature; hence, he can't be brought back from "dead" to "creature."