I really don’t want to fall off into this rabbit hole ... but none of the original citizens of the U.S. had parents who were citizens, because the country did not exist when they were born.
Thus it seems to me the requirement to be a natural born citizen was to be born on the soil of the nation.
Hence grandfather clause for eligibility.
Looking forward from that moment, each state had different laws for conferring citizenship. In order to be a citizen of the US, one had to be a citizen of one of the several states. If you were a citizen of a state, you magically became a citizen of the US at the moment the constitution was ratified.
Agreed about avoiding the rabbit hole. Glad that Cboldt pointed to the answer. Very curious that Q is pointing at this issue ... maybe doing so prods the enemy do stupid but revealing things.
The goal was to only allow those to be President that had NO SPLIT LOYALTIES to any other nation! Natural Born Citizens would never have dual citizenship, therefore could not betray the nation out of misplaced loyalty.
JMHO.