And by the way, it is hypothetical--we haven't yet had it happen so we haven't yet seen a court rule. When we do, bet that the court will hold the kid "natural born".
You can't have it both ways, one way having Wong Kim Ark using the 14th amendment to hold that anchor babies are "natural born citizens" for presidential qualification purposes, and the other way that no US Court has heard the issue.
I think the issue has never been before the Court, and that it is plain error to read Wong Kim Ark for the proposition that anchor babies are constitutionally qualified. But you opened with the remark that dual citizenship is irrelevant to the question of constitutional qualification, which strikes me as an entrenched position on the other side.
Anyway, I agree that the Courts won't hear the issue. I also predicted that Congress would shirk ITS constitutional duty of challenging and deciding qualifications, by pretending the issue was already decided (by magic, I suppose) at the time the electoral votes are counted.