Ok, what kind of information structure is that experience encoded in? This is where it's really easy to start thinking the brain is some kind of interesting magic rather than encoded information.
In the case of the brain the encoding is such that various functions "fall out of" it, like being able to relate experiences, etc.
There's no magic proposed here, this is a physicalist functionalist view.
Nothing about this prevents a computer from being sentient. As I said, none of this even matters. The key premise is that LLMs are trained on language and not experiences. Unless you believe that a description of an experience is identical to the phenomenal experience, then we agree on the key premise. Do you think that they are identical?