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A repeated message is not always a repeated decision
Two similar messages may represent one instruction or two. A reliable service makes intent and unresolved status explicit instead of allowing a convenient matching rule to decide.
When a response does not arrive, the caller has a business question: did the intended action happen? A technical timeout does not answer it. The action may have completed while the response was lost, or it may never have begun. Sending another message can be a sensible way to continue, but the service needs to know whether that message repeats the original instruction or starts another one. This distinction is easy to omit from an attractive demonstration because the demonstration usually shows a successful request followed by a clear confirmation. The uncertain middle is where the real service earns its reliability.
