Nice try at parsing but they are equating native born and natural born.
"We start from the premise that the rights of citizenship of the native born and of the naturalized person are of the same dignity and are coextensive. The only difference drawn by the Constitution is that only the 'natural born' citizen is eligible to be President."
[Article II; Section I]
No Person except a natural born Citizen, or a Citizen of the United States, at the time of the Adoption of this Constitution, shall be eligible to the Office of President; neither shall any Person be eligible to that Office who shall not have attained to the Age of thirty five Years, and been fourteen Years a Resident within the United States.
Now.....how many types of citizens are mentioned in this paragraph? Three? Four? No! Only two! Would that imply to you that there is a difference between these two?
If you answered yes.....what do you suppose that difference would be and why do you think this phrase was "grandfathered"?
Now......where does this paragraph speak of Naturalized citizens....the third type? It doesn't.
Justice Douglas is stating very succinctly that Native born and Naturalized citizens are very similar. But....only Natural Born Citizens are qualified to be the "Commander in Chief". If you believe he was equating "Native" born with "Natural" born.....then why does he use two different adjectives?
Now.....according to [Article II; Section I] do Citizens of this country cease to exist after a certain period of time? Of course they don't. They just no longer are qualified to be the "Commander in Chief" (if they were not yet born at the time of the signing of the Constitution)! After all the potential Presidential aspirants had died off after the Constitution was ratified....then normal citizens (which they had been) were no longer allowed to be "Commander in Chief".
They had not been born to U.S. Citizen parents....so they were not called "Natural Born"....only "Citizens" (Native Born) and that how Article II; Section I] defines them......Citizens! But until they had all died off the grandfather clause still allowed them to seek the Presidency.
Thus...............Justice Douglas in his opinion has identified all three types of Citizens and very pointedly has indicated......only "Natural Born Citizens" were qualified to be President.
At the time the Constitution was written native born and natural born meant the same thing.
Really!!! Then please explain these words of Justice Waite in Minor vs Happersett:
“The Constitution does not, in words, say who shall be natural-born citizens. Resort must be had elsewhere to ascertain that. At common-law, with the nomenclature of which the framers of the Constitution were familiar, it was never doubted that all children born in a country of parents who were its citizens became themselves, upon their birth, citizens also. These were natives, or natural-born citizens, as distinguished from aliens or foreigners. Some authorities go further and include as citizens children born within the jurisdiction without reference to the citizenship of their parents. As to this class there have been doubts, but never as to the first. For the purposes of this case it is not necessary to solve these doubts. It is sufficient for everything we have now to consider that all children born of citizen parents within the jurisdiction are themselves citizens.“