[BuckeyeTexan]

As it has been explained to me by a conservative history professor, while the initial intent may have been different, subsequent court decisions have defined “natural born citizen” as to mean an American citizen at the time of birth. 

That would be incorrect. NBC remains, to this day, distinctly undefined by the courts. Even the State Department is not clear on the definition.

According to the Foreign Affairs manual published by the U.S. Department of State, statutory citizenship (i.e. granted by U.S. statute at birth) may or may not be equivalent to natural-born citizenship under the U.S. Constitution.

7 FAM 1131.6-2 Eligibility for Presidency
(TL:CON-68; 04-01-1998)

a. It has never been determined definitively by a court whether a person who acquired U.S. citizenship by birth abroad to U.S. citizens is a natural born citizen within the meaning of Article II of the Constitution and, therefore, eligible for the Presidency.

(...)

d. (snip) In any event, the fact that someone is a natural born citizen pursuant to a statute does not necessarily imply that he or she is such a citizen for Constitutional purposes.

[DiogenesLamp]

That would be incorrect. NBC remains, to this day, distinctly undefined by the courts. Even the State Department is not clear on the definition.

You want clarity on the definition? How about you look to the foundational theory of the document which created US Citizenship?