There is a small, but legally significant, subset of persons born in the U.S. who are not U.S. citizens. Therefore, a claim of birth in the U.S. is insufficient to establish an allegation of making a false claim to U.S. citizenship, unless DHS can allege and prove that in the particular case, the same benefits could not have been obtained by someone born in the U.S. but who was nevertheless not a U.S. citizen. Thanks to David Link.