That is the only part of what you posted that is relevant to a specific determination of citizenship status. It supports what I posted before. There final decision, based on definitions of "natural born citizenship," established in Minor v. Happersett, was that someone born of foreign citizens on U.S. soil was "native-born," as opposed to the classification of "natural-born."
I don't see how anyone can say that SCOTUS has not definitively ruled on the issue. They weren't trying to say the subjects of either case was natural-born but in the process they did define it.
Yes, both Wong and Minor used this defintion of natural born citizen: "all children, born in a country of parents who were its citizens." The modern case, Ankeny v. Daniels, acknowledges that Wong Kim Ark did not declare its plaintiff to be a natural born citizen.
Because the Court has only discussed the issue in dicta. Natural-born has never been part of a Supreme Court decision's central holding therefor precedent (and stare decisis) isn't established. Dicta can be used for lower courts and the Supreme Court as persuasive precedent, but not binding precedent. So, they can weight it, but they're not bound by it.
If you want a better, more detailed explanation, an Illinois law professor, and one of the foremost authorities on semantic originalism, Lawrence B. Solum, wrote a piece that appeared in the Michigan Law Review several years ago. It can be found searching google with those parameters.