Bike guy, I have a couple of thoughts. There may be some internal stress if there is a lot of coming and going in your rabbitry. You may not be aware of it. Species differ greatly in how they ‘react’ so just because you do not see rabbits behaving as you would expect from visual observation and your human experience does not mean that they are not ‘reacting.’ Rabbits and humans are so different in terms of their taxonomic relationships. Then again, if your rabbits in general live a stable, stress-free life with not a lot of turnover, they may not mind at all.
Second, keep in mind that we have different senses (sight, hearing, communication, vocal chords) and different social relationships than rabbits. You cannot expect them to have a human reaction to death or loss. They do not have vocal cords like humans to cry and wail, and more importantly they do not have an evolutionary past that relies on longterm social/communal relationships for survival, like humans. Their evolution likely selected for individuals that breed quickly and often to make up for high losses due to predation. Therefore they did not likely evolve strong emotions to worry about death as much as we do. It would be a waste of energy for them to grieve like we do. We are a longer lived species with much longer development and slower growth rate, and one individual human is therefore more important for population persistence. It makes sense that we should be a lot more stressed about the possibility of death. Thus, their response is likely to be different than ours even if they are aware of death. In your particular case, it sounds like they may not be aware of the butchering process.
Overall, be cautious in how you interpret rabbit behavior. Keep an open mind. Also, do not view one species as superior over another due to so-called intelligence (which is always defined in humans terms) or sensory ability or evolutionary past. We are all different, with different strengths and weakness, and I am glad of my rabbits and what they give to me.