I would throw the BS flag. I was in electrical contracting for 7.5 years. I think the NEC (National Electric Code) can be pretty stringent on things, so I don't know how an appraiser could dictate more stringent rules. I would challenge him to show you wording in the FHA Law where that is necessary or get his supervisor involved.
Sounds like someone needs an ego stroked. Or if he is that insistent, I would put it on the buyers to square up those costs.
Maybe you can post your question here: