We don't run our own unit tests on compiled code because it generally can be trusted. LLMs are an extraordinarily leaky abstraction.

Saying "as long as it works and tests pass" suggests that we can test for every possible scenario. We can't. And tests can be flawed on top of it. Which is why an LLM is no more a compiler than a human coder (as you say) is.

The exact same can be said for human code... so what's your point?