The report should have been CB4'd subject to that inspection. If someone wants to require them to crack it open that is their call, I am only following FHA/HUD guidelines. If they wish to waive it that is fine as well.
Remember, in every case and in every instant it is the golden rule: Those with the gold make the rules. It does not matter if to you it is unreasonable, it is what it is. Now what you have on your hands is not only an error on the report but based on what has been posted by others in your local market, a potential code violation. And remember you are not the bad guy here. It is a requirement in order to qualify through FHA/HUD. If the owner doesn't want to do it than they must not really want the loan.