If you were on a real flight and asked a human for help, they wouldn't give a deterministic answer. This doesn't seem like an actual requirement that is needed, but rather something that is post hoc rationalized because it was cheaper to make that way. While terms like consistency may come up when referring to having deterministic output as a requirement, the true reason could actually just be cost.
The bank can very much determine if the payment has been made or not (although not immediately, as you mentioned). As a rule, banks like to keep track of money.
Yes it settles deterministically. With AI it claims to be settled and goes on, and it's up to you to figure it out how deterministic the whole transaction actually was.
Is it the main issue? Payments suffer from race conditions, but the processes themselves are deterministic, auditable and may be rolled back. Not sure how many of these important attributes would remain with a neural network at the helm.
Even then it can be deterministic but not explainable. Tfidf is fairly explainable but about the limit imo for full explanations making sense such that you can fully reason about them and predict outcomes and issues accurately. Embeddings could give better, fully deterministic results but I wouldn’t say they’re 100% explainable.