Originally Posted by
Endus
You've cited nothing to suggest this is the case.
The "always act as if the weapon is live" is literally impossible in many circumstances; in military training exercises, for instance, or, yes, on film sets. It's a good basic principle for general firearms handling, but it is not a universal truth for all circumstances.
Much like principles like "don't stick anything metal in a socket plug" makes sense, as a general principle, but if you're an electrician or otherwise know what you're doing and are effecting repairs with proper safety protocols, you can ignore that, and indeed, have to in some cases.
Or "don't lick other people under any circumstances", which makes sense when you tell that to your 5 year old, but will probably hurt their dating life as an adult.
Folksy maxims aren't legally binding descriptions of liability.