They are black boxes, and can even use the same NN architectures as the generative models (variations of transformers). They’re just not trained to be general-purpose all-in-one solutions, and have much more well-defined and constrained objectives, so it’s easier to evaluate how their performance may be in the real-world (unforeseen deficiencies, and unexpected failure modes are still a problem though).
Key word is “serious.” Overstaying a visa visit is a civil offense, not even a criminal misdemeanor where the punishment may just be a small fine.