Bob,
I would normally agree with your code quote, but I was thinking .....
Since there is no requirement to provide receptacles in the restaurant, who is to say that the flexible cord is acting as a substitute for the fixed wiring of a structure.
Thinking about it another way, if a 6' cord was installed on a lamp to reach a receptacle, using the logic in your response, wouldn't that also be considered as a substitute for the fixed wiring of a structure? A receptacle could be installed at the lamp! [Linked Image]
I don't know the answer, I'm just being critical.
I've never found a limit to a cord length written anywhere (except 645 for IT equipment)

Ron