Looks to me as if the rough draft didn’t pass muster, and they realized they had to change the qualification from merely, ‘born a citizen’ to ‘natural born citizen’. In that day and age, people knew exactly what was meant by NBC; it was common knowledge. The Framers didn’t forsee a time when ignorance would be so rampant and post-modernism so pervasive, that people would have no grasp of history and words would mean whatever a liberal says they mean.
Good find.