Funny-hope the inspector thought so, or the bosses next few jobs are going to be nitpicked to death.
I certainly have questioned the labeling requirements. OSHA requires electrical panels to be opened only by qualified personnel. One would have to think that part of being "qualified" would include understanding both shock and arc flash hazards present. Routine, redundant labeling usually gets ignored-I see no point in it.
However, the inspector might have had a legitimate concern. Labels that specifically quantify the level of hazard are usually required in commercial installs. If he tried to get away with a generic label because he did not want to, or did not know how to, do the calculations, the inspectors response is legitimate.