Warlock methods for creating Death Knights were primarily intended to give physically frail spellcasters a powerful body, creating formidable units capable of fighting at any range.
As for whether that body was dead or alive, that truly did not matter. So long as the body was empty and had room for the incoming soul, it would do.
Bio-cradle technology had originally been used to repair damaged human tissue, like patching a broken spot on a doll with an identical replacement. Restoring missing limbs, or even vital organs and the nervous system, was no problem.
However, while this technology could indeed completely recreate a human body, the resulting body was somewhat like a case of brain death. From a purely biological perspective, all its tissues were perfectly alive. With outside assistance, it could maintain a heartbeat, breathing, and other signs of life, but the moment the tubes were removed, it would die immediately.
Put plainly, it was an empty shell without a soul. Bio-Cradle technology, something akin to 3D printing, could perfectly print a body, but it could not print a soul. Otherwise, Evenson would have long since had Helen Zhao running at full capacity, mass-producing people who rolled off the assembly line like dumplings, letting him harvest souls one by one for an inexhaustible supply of soul fragments.
Thus, Ancient One's newly recreated body was alive, but it was also an empty vessel waiting for Evenson to place her soul inside. Because of that, she had become the unprecedented and, so far as was known, only living Death Knight.
But to be clear, the Burning Legion, the origin of Warlock magic, was certainly capable of producing similar results. They might not have Bio-Cradles, but restoring activity to a corpse was effortless for them.
The main reason was simply that they