I think they would have noticed that his parents were citizens.
since he was born to them— he would be a natural born citizen.
They would also have written language stating that individuals must be born within the borders of the United States.
Our laws are based on English laws in every state but Louisiana, which is based on Napoleonic law. The British considered any children born to an English citizen to be a British subject no matter where they were born, and even if only one of the parents was an English subject. Our founding fathers held similar views, and they would have considered Cruz as a natural born citizen since his mother was an American natural born citizen.
None of our Founding Fathers were born in the US.
At no time would a person born to an alien father in a foreign land be considered a natural-born citizen of the United States.