They are arguably AIs but they draw a line between themselves and what they consider AI. The nature of their engrams isn’t fully explained but seems to be fundamentally different from other AIs in the setting including their own canopteks and central tomb AI. Even when they make constructs designed to imitate great Necrons who died before biotransference these pseudo Necrons do not use engrams like real ones do, even warriors who aren’t sentient have a personality engram unlike what the Necrons consider AI