Yes, if I were in the original position and there was a chance I could be born into a life of being treated like property with no autonomy and completely incapable of improving my lot in life, that would be unacceptable.

From the original position it doesn’t matter how you interact with a society, if the society affects you it is relevant and worth considering from the original position. For a human-to-human example, a slaveowner could use that logic to say that slaves aren’t members of society so therefore the original position doesn’t extend to them. But it does extend to them, they are affected by the society even if they don’t get to make decisions about how it operates or interact with it freely, the society’s norms, values, and what it accepts heavily influences their life and experience of the world, and so they are very much worth considering from the original position. From the original position, there’s a chance you could be the one born under the heel of societies boot, and that society might not view you as part of their society and use that to justify your abuse and exploitation. All the more if you’re not human and can’t advocate and fight strategically for your own freedom the way humans can

Edit: obviously a human slave, once freed, would be able to participate in society in a way that a nonhuman animal couldn’t, but even then there are humans with severe brain damage or severe mental illness who would not be able to participate in society much. From the original position they matter too, even if they can’t participate in society or be held responsible for things