The problem isn't non determinism, but that changing a single token in the input can change the output completely. And you can't put that somewhere in production completely unattended.

It's the uncertainty of "who knows what the machine will output this time" if you have no idea of what the input is going to be.

Exactly. Doesn’t matter as much for coding, where there is a human in the loop at some point. It does matter if you want to take the human out of the loop.