Joseph Story, Commentaries on the Constitution 3:§§ 1212--22
Your link is with regard to citizens of the United States resident in DC. Most of them, at the time written, presumably were born in one or other State. On leaving DC and moving to a State, they became citizens of that state as soon as they met the residency requirements.
Please explain how your link is relevant to whether Dred Scott, or any other black man, was forever incapable of being a citizen of the United States, now and for eternity.