All replicas are mere approximations. The question is if it's good enough. The magical thinking is in saying that because no replica is perfect it must be missing something important. What important property of an ant cannot be replicated in robo-ant?
Well, with an ant, it's a bit of a different story compared to sentience. Now, all animal behaviour can be mimicked or replicated using information theory. So, with an ant, there's no real difference. Bio-ant will act like robo-ant.
But with sentience, it's possible to replicate its
appearance. The problem is that we don't know what confluence of physical forces are necessary for
sentience. Does it require information processing at the level we see with neurotransmitters (which is quantized at the vesicle level)? Does it require a specific overlap of EM fields? We just don't know.
The one insight might be to acknowledge the uniqueness of qualia. A qualia contains a great deal of information about the environment (i.e., 'red' gives you insight into the energy of the photons hitting your retina), but it also contains an informational
je ne sais quoi that we just cannot seem to be put into informational form. How many bits are required to get you to imagine the same shade of red I'm currently imagining? We don't really know, but it's a
lot.
Does the sentience organism therefore
de facto contain more information than we think should be achievable through simple programming? So, an AI passing the Turing Test might be conversant, but (if it lacked sentience) cannot access the extra dimension of information contained within a qualia.
That said, our sentience is so utterly coarse compared to how much processing is going on inside our brains. It could be that sentience doesn't give any additional insight.