There’s no question that he’s naturalized. Without statute he would not be a citizen.
The foreign-born child of a U.S. citizen mother in 1874 was not a U.S. citizen.
The foreign-born child of a U.S. citizen mother in 1970 may become a U.S. citizen, provided conditions are met.
Exact same circumstances, completely different outcomes.
In 1970 there was a Congressional act which provided the foreign-born children of citizens may become citizens if the terms of the statute are complied with, in 1874 there was not.
To illustrate, a child born to a U.S. citizen mother in 1874 in Oxfordshire, England was not a U.S. citizen. That child is Winston Churchill, he was posthumously proclaimed Honorary Citizen of the United States April 9, 1963 (Pub. L. 88-6)
The exact same circumstances as Cruz, the foreign-born child of a U.S. citizen mother, yet Churchill was not a citizen. Why? Because there was no statute to make him one.
I don’t know if you have ever heard of this, but occasionally Congress will pass a statute that is quite out of alignment with the Constitution.