> is already fully solvable with structured output.

Not particularly. There is still the problem of hallucinations and varying results across runs.

That's more of what type-safety means for their team. Every run gives the same results. It's type-safe

This seems like an unusual definition of type safety. I certainly understand how every run deterministically giving the same schema (type) of data is a requirement to be "type-safe", but in my mind the content of the result is not relevant to the question of type safety. Am I not getting it?

There's still run-to-run variance because it's not fully deterministic. So runs with exact same inputs can return different outputs. Besides, though the output always conforms to the choices you specified, whether the probabilities attached to them are actually correct is a different issue.