IMO the inspector should provide the calculation to prove that the 40% fill has been exceeded. Won't happen but given the blatant display of ignorance it should happen.
FWIW...
I've noticed that some panels of similar vintage say something on the label along the lines of "This enclosure complies with the wire bending space requirements of the 1980 NEC." Or some such. If the panel label still exists it might be worth peering at it to see if it says anything like that to help you make your case.
(This is not to say that older panels do not necessarily also comply.)