If a “citizen at birth” by naturalization statute is (as you contend) a “natural born citizen” at the time of the Adoption of this Constitution what would be the point of Article II’s distinction of “citizen” and “natural born citizen”?
Or are you contending that a citizen necessarily encompasses “naturalized citizen” as well as “natural born citizen” EXCEPT at the time of adoption?
Two classes of citizens are eligible to be president:
• Natural Born Citizens over the age of 35
• Citizens at the time of the adoption of the Constitution who are over the age of 35
The point of the second class is that the first class was a null set in 1787. There is no broader implication of the kind you're trying ineptly to draw.