I've thought about it more and I think another problem with LLM non-determinism is the "prompting" problem. You can rephrase the prompt very slightly and bias the model in a completely different way. The randomness in the output for the same prompt is one thing, but the randomness in the input is a completely separate problem and can't be ignored. It leads to a lot of mysticism about "oh yes, I am a prompt master, only I can prompt properly" (true or not).