Then he is a dual citizen, inherited from his father, not NBC.
Anyone granted citizenship at birth by another nation - even if born to two U.S. citizens on U.S. soil - would be ineligible for the Presidency according to your ‘reasoning’.
Most of our founders were natural born subjects of England according to English law. England considered all Americans subjects of England - thus their impressment of U.S. sailors on the high seas - until the war of 1812 decided the issue.
Was any American born between 1776 and 1812 not eligible for the Presidency because England considered them as English?