FWIW, those manuals have no force of law. Plenty of manuals are mistaken. In fact, it’s not a bad assumption that any statement in a government manual is false, and seek statutory and case law. Definitely do that if the issue is important.
“FWIW, those manuals have no force of law.”
Of course, but they do have some probative value to ascertain the interpretations in use at a point in time. The quote also demonstrates the acknowledgement that the Constitution and its usage are acknowledged to take precedence over anything found in the Foreign Affairs Manual.