because citizenship issues are delegated to Congress
Naturalization issues are delegated to Congress. Their power is limited to establishing a “uniform Rule of Naturalization”. They have no power to redefine Constitutional terms.
Your quotes talk about twi *sources* of citizenship, by birth and by naturalization. Natural Born is not a source of citizenship, it’s categorization of “by birth” citizenship. Natural Born Citizens are just a special subset of “citizen by birth”. . It is of course a large subset.
But your quotes have nothing to do with the requirements for Natural Born Citizenship, one way or the other.
Despite what lawyers might think, not everything is to be found in precedent. Especially true with regards to the Natural Born Citizen meaning, because it really only comes up in eligibility for President. There is no other situation where a "born in the US of alien parents" is treated any differently than a "natural born citizen". But regarding the the notion of Congress only having power over naturalization, but not citizenship per se, yes, I have at least one court case. Fairly recent too.
Rogers v. Bellei, 401 U.S. 815 (1971) The case distinguishs not only between "Naturalized" in the US, and "naturalized" elsewhere. It puts a person born to a US citizen parent, overseas, who was granted a US passport and status as a US Citizen but who then failed to perform the necessary final declaration and residency, in order to retain that citizenship, on a different footing than someone naturalized "in the United States". The distinction being base on the language of the 14th amendment.
It mentions that even the pre-1934 distinction between the child of alien father and US mother, vice a child of a citizen father and alien mother, was a legitimate exercise of the power to define a uniform rule of naturalization.