The four women were originally built as full-body companions. The modification that made them dangerous came later and had nothing to do with turning them into disciplined soldiers. Someone took the visual system that once watched a client's face, breathing, body temperature and arousal and grafted a new recognition routine onto it.
Juno might be laughing when it happens. Celia might have been fixing her hair. Mirei might be halfway through a sentence to another doll. Sable might be complaining.