All four of my grandparents were born 1893-1896 in the United States (NY x 3, Connecticut) to alien parents.
When my grandfathers registered for the draft in 1917, there were 3 and only 3 citizen options: Natural-born, naturalized, and alien.
Both of their draft boards registered them as “natural born”. They certainly were never naturalized. If they were aliens, then both of my parents would be aliens, too, under this theory, and since both of my parents would be aliens, I suppose I would be as well.
How does this fit with this theory?
Good question. The immediate answer is that it doesn't seem to fit but may provide an instance of governmental confusion.
Somewhere there is a CD with the WWI draft registration form of one of my ancestors, but I will take for the moment your assertion that the only form of citizenship recognized by a WWI draft board was NBC and naturalization.
The founders clearly recognized, however, by virtue of language used at the time presidential qualifications were set out in the Constitution that there were two separate forms of citizenship: mere "citizenship" and "NBC" (naturalization not yet available in the newly born country).
That same language inasmuch as specified the NBC requirement would kick in after a specified number of years because a NBC candidate would only be created by parents who were born on or after the date of adoption of the Constitution.
What was the purpose of such language?
How does that fit into the "regardless of parentage everyone born in the country is a NBC"?
Wouldn't be true that if this latter viewpoint was controlling there would have been no need at all for any discussion by the founders of NBC?
“How does this fit with this theory?”
Simple. The miltary wanted men.
They were naturalized.
Your grandparents were naturalized at birth via the 14th Amendment.