That is not naturalization. The law clearly states that they are citizens at birth and defines naturalization as "the conferring of nationality of a state upon a person after birth."
The certificate is even called "Consular Report of a Birth Abroad of a Citizen of the United States of America." (I have two of them in my fireproof box at home.) It doesn't confer citizenship, it documents the citizenship that existed from birth.
Interesting, its a sticky subject for sure. I think that we are treading on dangerous ground by allowing the broadening of the definition of natural born citizen to move away from two citizen parents on American soil(or out of the country on the Nation’s business).
Some will argue that citizen at birth is the same, which my reading of the Constitution, Founder’s documentation and court decisions doesn’t support. So whether we use semantics to state that the citizenship is present at birth and recognized later or whether the conditions of citizenship are deemed to have been met and citizenship awarded, doesn’t really change the fact that that kind of citizenship is not Natural Born citizenship which is citizenship conferred naturally since no other citizenship was possible for the individual.