It is difficult to reply without making assumptions about how you (or the argument you are referring to) uses 8 U.S.C. § 1401 to support eligibility for Cruz, so please correct any of the points below that may be incorrect. The argument you are citing / suggesting / making would be something like this:
1. Cruz (and his mother) fall within the conditions in 8 U.S.C. § 1401(g).
2. Given that Cruz (and his mother) fall within the conditions in 8 U.S.C. § 1401(g), 8 U.S.C. § 1401 provides that Cruz is a "citizen[] of the United States at birth".
3. A "citizen of the United States at birth" is a "natural born citizen" under Article II.
4. Therefore, Cruz is a "natural born citizen" under Article II.
Sorry, don’t want to play this game. Bye.