Calling an extension cord temporary wiring is, IMuHO, an absurdity. You will have a tough time convincing me that the intent of the Code Making Panel was to apply the rules for "Temporary Installations" to UL listed extension cords. I just cant see the laying out of an extension cord as an "installation." I think that this issue is ripe for a formal interpretation.
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Tom H
IMuHO = In My unHumble Opinion. If it were merely my humble opinion would I even utter it let alone defend it?