Defining natural-born citizen is inherent to the act of establishing a uniform rule of naturalization. Congress must determine who does not require naturalization in order to establish rules for those who do.
Similarly, Congress must determine what is legal in order to establish rules for that which is illegal.
Nope.
"Natural Born Citizen" was already defined when the Constitution was written as were other words such as "the People", "The States", "Infringe" and all other terms in the Constitution. None of these words were present in the Constitution as place holders waiting for Congress to decide what they meant.
The problem is many people don't accept the only logical definition of NBC.
Clearly a NBC is not a person born when an American man travels to Russia and gets a member of Vladimir Putin's family pregnant. OR, any other situation where only one parent is an American citizen and the baby is born on foreign soil.