There's the answer, the wiring system will not collapse prematurely as the structure it is attached to will be in a state of collapse already by the time PVC cleats fail.
Also while no mention of the type of building, the intention is to prevent entanglement of emergency response personnel if they enter a building with a collapsed wiring system.
No firefighter is going to enter a shed other than to rescue a person and I can't recall there being a single case of shed based self immolation, so the whole discussion is moot.
Well it's mootier still as, in the infinitesimally small chance that a firefighter does enter and become entangled, who can prove what failed first and where.
This is so nonsensical I'm wondering if it's trolling?