How can a child who did not sneak in be considered ‘under the jurisdiction of their homeland’, a country they have never set foot in?
The law doesn't say "under" it says "subject," which, given that I posted a link to an 1856 law dictionary above AND that definition is in the article you clearly didn't read, renders your "question" baiting and misdirection on a foundation of ignorance.
Nationality law. For example, the British Nationality Act of 1948 establishes worldwide jurisdiction in the matter of British nationality. Obama was born under the U.K.'s nationality jurisdiction.
Much like the U.S. has established worldwide jurisdiction over its citizens in the matter of being required to pay federal taxes on their income regardless of source.