I can even give them all my tax money, but if I also give them a list of items they deem to be a tax deduction, they will give me my money back. I don't even need to really ask for it except by putting it in the paperwork. I don't need to say "and therefore I believe I have overpaid by £X".
The problem is two closely related issues, IMO... First, these rules are probably too broad/vague and easily abused. And second, it's too difficult/costly for the IRS to successfully challenge when a company does abuse these regulations.