Dying in one step isnt the point of a deadzone level, those are poorly written levels that miss the point of the survival difficulty. Deadzone levels are strictly unsustainable and don't have a working strategy to survive them, they also usually have a single dominant entity type that is the cause of the danger. The survival difficulty "habitable" is unnecessary, but writers understand what that means more and no one complains about it
You're going from the thought that one could live for long enough to document the level over radio commands. At that point, if they could live for that long, the level would not be a Deadzone, but rather, a Class 5 or lower.
I think that people just can't understand how a scale works, they just need something above the scale to prove that their levels are dangerous. It's not like 5 is already high enough, they just need to keep going.