From what happened in the second episode with Morrow shows that aliens respond differently to cyborgs. If that had been a human they wouldn't have survived! I feel like synthetics as well would be of even less interest to the aliens than cyborgs as there's no physical part of them thats human and thinking back over previously films, I can't recall a time when a xenomorph killed a synthetic that wasn't just getting in its way. Of course we can see how Kirsh gets on!