Also, Stompy in Alien: Isolation ignored the Working Joes. David's not technically alive or organic. Perhaps the neomorph's behavior is an extension of the bio-weapon itself, which is designed to attack animals, and not plants, thus explaining the carnivorous nature of the beast? But if David is not organic, would the weapon even effect him, in any shape or form, be it ampule, bomb, spore or neomorph?