Determinism only helps if you always ask the question with exactly the same words. There's no guarantee a slightly rephrased version will give the same answer,

Determinism only helps if you always ask the question with exactly the same words. There's no guarantee a slightly rephrased version will give the same answer, so a certain amount of unpredictability is unavoidable anyway. With a deterministic LLM you might find one phrasing that always gets it right and a dozen basically indistinguishable ones that always get it wrong.