I don’t want to get in the middle of a heated debate, but I have always seen it the way Don is explaining it.Wow that is interesting in NFPA 72 the manufacturer's instructions over ride the code almost 100% of the time with few exceptions
If a manufacturer tells you that their product has to be wired up with 18 gauge zip cord connected to a 30 amp breaker, we can’t do that. Now that is exaggerated for illustrative purposes, but isn’t it the same thing?