I think that by debating what consciousness is not is one of the best ways we can gain a deeper understanding of consciousness itself.
The weird thing is, you and Chiang have different arguments but you're using the same logic:
> Before anyone can credibly claim that they’ve solved an extraordinarily difficult engineering problem, I need to be confident that they have previously solved the many much simpler problems that precede the difficult problem.
IOW if we don't know what consciousness is, how can we call LLMs conscious when we haven't seen even the barest intermediary steps towards our nascent concept of consciousness first?
I think it's telling to your point that when Chiang describes what would make him think an LLM was conscious he starts using words like "believe" and "want" right away, because yeah as you say, we have no qualifications for what consciousness is.