It's not illegal and its not in violation of FDA rules. That disclaimer text is from a specific law that gives them exemption from those rules: https://en.wikipedia.org/wiki/Dietary_Supplement_Health_and_...

It's not a manpower issue, it's not a legal issue. It's not against the law because they wrote the law. There is no line they try to avoid crossing because that line was erased by lobbyists in 1994.