It's ok, they unplug it every Sat night. So, it's only used for 6 days.
U.S. Office of Compliance appears to only deal with the workplace, so their standard probably doesn't apply here. From looking at their page, they seem kind of like OSHA. And, I am sure OSHA has something to say about extension cords too.
Is the NEC even "law" in that sense of the word? If I (homeowner) do something that it says I can't, what happens? Obviously, I could fail a inspection if there were one for work being done. Not sure how that is or could be applied to or enforced with homeowners.
Who would enforce it? Building inspector? Fire Marshall? SWAT team? Dog Catcher?
I would bet in some form or another, most of us have some violation of the NEC. If it were enforceable against homeowners, I am sure they would have seen it as a revenue stream by now and would at least be trying to enforce it at some level.
And, yes, I am ODD and I do buck the system and question everything like this. Not just being difficult, just me.