It's a common thing to find a film review of Kubrick's 2001 in which the critic says the most human character in the movie is HAL 9000. Are they so dumb that they don't realise that HAL is an AI, only a bunch of inscrutable CCTV lenses and banks of computers? He doesn't even have arms or legs, how could he be considered human? But of course, they are talking about the way HAL has a mind resembling that of a human. In a story, that's all that matters.
It's a broader definition of the meaning of 'human'. It's why we have whole stories about characters that are rabbits living in the Berkshires of Southern England, characters that are white-tailed deer living in a forest, characters that are toys, characters that are cartoon flying elephants, and yet they can emotionally involve us in their lives and even bring us to tears. Why is that? How does that even work? It's because within the story these characters have the functionality of human minds, they are anthropomorphised with the same types of thoughts and feelings and emotions and motives and goals and desires that are familiar to us in our real life experiences with real live humans. It's not what they look like, it's their minds that count.
And so it is with the robots in the Alien films. As characters we relate to them as human, despite the fact that we know they are not literal humans.
For example, even after we know that Ash is a robot, because he is now a talking decapitated head, we still look for human nuance and hidden meaning in everything he says and the ways he says it, because to us, as a story character, he is still a human. We detect pride, resentment, grandiosity, and menace in his words - human qualities that we would expect from a human character in his position (were it logically possible, being a decapitated head n' all).
Bishop seems innocent and servile. But knowing he's an android means we are constantly suspicious of his motives, waiting for his true intentions to be revealed. We read his personality, his facial expressions, the way he delivers his dialogue, his behaviours, in order to mentally read his secret inner thoughts and feelings. Actually, everyone in the movie gets exactly this same treatment; whether they are human or robot or animated rabbit doesn't matter, as far as the storytelling is concerned, they are all functionally human.
Spoiler
Actually, we do this in every movie and TV show we ever watch, whether we realise it or not. In fact, we do this in real life, with every real life human we ever meet. We can't help it, our brains and our psychology evolved to do this automatically. If you want to learn more you can read this book:
https://www.amazon.com/Science-Storytelling-Stories-Human-Better/dp/1419743031James Cameron knew this. That's why Bishop is set up the way he is. We know about that early draft of
Aliens (I think it's the scriptment) in which Bishop pilots the second dropship down to the colony in order to fly the survivors back to the safety of the Sulaco. But as he's about to touch down he radios Ripley and apologises for his programmed behavioural inhibitors that prohibit him from landing because to do so would endanger other human lives with the threat of Alien infection. And with that he flies away again, leaving them high and dry.
Clearly, Cameron thought better of this in the rewrite, but why? I can only guess, but I think he didn't like what that said about Bishop as an AI. In that version, Bishop had no free will, therefore no agency, and therefore was not human enough for Cameron's taste. Bishop is already clearly discriminated against as a mere android: remember the "That's right, Bishop should go!" scene? This is also the scene that shows Ripley's growing understanding of Bishop's true humanity. Look at her face when he volunteers to crawl to the uplink tower; it's one of respect and admiration, because she knows selfless altruism when she sees it. And what about Bishop's self-effacing explanation for volunteering? He says he has no desire to sacrifice himself, that the decision is one of logic, but Ripley, and we, know better. We didn't sneer at Bishop's bravery, thinking that he's just a machine performing a calculated decision. No, as I've explained, as an audience we treat every character that shows signs of a human mind as a fully fledged 'human', just as Cameron knew we would.
This scene, and the way Bishop shines through in the climactic ending, tells me that Cameron is saying that androids can be worthy people too. This is only a subplot and subtheme, however. It does not have primacy. But it is clearly an issue Cameron wanted to address - that of an AI or android's right to personhood. It shouldn't be much of a surprise, really; it's a common sci-fi theme.
I could go on about all the other androids in the Alien films, but shit, my posts do seem to drag on sometimes...
TC