LLMs are not non-deterministic by design. The randomness in the output is artificially injected for ergonomic reasons. (Yes, the non-determinism in production systems is different, but also not by design)
You don’t train calculators on how to add. All calculators will more or less come up with the same answer to some deterministic and quantifiable level of accuracy and precision.
You're missing the forest for the trees here. The point OP is trying to make is that calculators originally were essentially non-deterministic. Technology will go from unreliable to reliable.