I think we're looking at the matter of scope.
In an industrial setting, the point where the electrical circuit ends and the appliance begins isn't always so easy to define- especially when several machines are interconnected.
There are other authorities to look to. OSHA has jurisdiction, assuming the firm is "large enough to affect interstate commerce."
Much industrial equipment is custom-made for a particular process. The equipment manufacturer has a very large say in what should be, and often the info is available on the web.
Even where there are "exempt" areas (utilities and mines, for example), there are other standards that can be referenced. Often present management with copies of the appropriate standard will be enough to make them see the light.
