Still not quite grasping the "or naturalized" authority part are you.
To naturalize in the 60s you had to apply for a green card, start the immigration process, renounce your home country, and swear fealty to the US
That process took 10-15+ yrs back then.
Kamala’s father naturalized (ie: completed the process) in 1981.
All it takes is one parent to still hold foreign citizenship upon a child’s birth and that child would not be a natural born citizen.
It’s very straight forward which is why the Founders chose those words.