If we defined "LLM" as "any deep learning model which uses the GPT transformer architecture and is trained using autoregressive next-token prediction", and then we empirically observed that such a model proved the Riemann Hypothesis before any human mathematician, it would seem very silly to say that it was "not intelligent and not capable of reasoning" because of an a-priori logical argument. To be clear, I think that probably won't happen! But I think it's ultimately an empirical question, not a logical or philosophical one. (Unless there's some sort of actual mathematical proof that would set upper bounds on the capabilities of such a model, which would be extremely interesting if true! but I haven't seen one.)