Imho there's also a clean argument against the existence of LLM-understanding: chatbots have been unable to summarize to experts (see my reply to you in the other thread) their own findings.

Even after prolonged interrogation. They were unable to _compress_ their own findings. Thus they might not actually understand what they have actually done. (They might barely pass an oral thesis defense)

(One may object-- that proofs aren't data that can be "compressed". But then doesn't the process of abduction generalise the very idea of data? to.. ?)