False Hawaii Missile Alert Sent After Drill Recording Said 'This Is Not A Drill' (npr.org)
A false ballistic missile alert in Hawaii was sent on January 13 because an emergency worker believed there really was a missile threat, according to a preliminary investigation by The Federal Communications Commission. From a report: The report finds that the false alert was not the result of a worker choosing the wrong alert by accident from a drop-down menu, but rather because the worker misunderstood a drill as a true emergency. The drill incorrectly included the language "This is not a drill."
You have missed the point of your own argument. By your argument the real message and the test one should be worded mostly differently so that there is NO confusion. The problem here is that the test message contains a message, a moniker that the message is not a test message, and a moniker that it is a test message. That's madness! In order to convert the test message to the real message you remove some extra words, which, as you say, easily causes confusion. The test message should be something like "in place of this message you would hear information about the real emergency". That is sufficient to test the system and will never be confused with an actual emergency message. I hear that sort of thing all the time on government and institutional warning systems. It really appears that whoever is in charge of this warning system in Hawaii really has insufficient expertise in this area.