First I’ve heard of that.
The issue was always where Obama was born.
If he was born in Kenya or Indonesia, his mother’s age would’ve determined his eligibility.
Read section "7 FAM 1133.2-2 Original Provisions and Amendments to Section 301" in this State Department document: http://www.state.gov/documents/organization/86757.pdf).
...(a) The following shall be nationals and citizens of the United States at birth: (7) a person born outside the geographical limits of the United States and its outlying possessions of parents one of whom is an alien, and the other a citizen of the United States who, prior to the birth of such person, was physically present in the United States or its outlying possessions for a period or periods totaling not less than ten years, at least five of which were after attaining the age of fourteen years...
Obama's mother was eighteen when he was born. The requirement was for at least five years after age 14. She was one year too young to have conveyed her citizenship to her son if he had been born outside the United States.
If Obama was born abroad of a citizen mother and an alien father, his citizenship depends on a statute. The statute describes the circumstances of birth that create citizenship. The circumstances of Obama's birth don't satisfy the statute in effect at the time Obama was born.
I don't know why people think that matters either. Congress can (and has) retroactively changed the citizenship law. Congress could pass a law that has the effect of making a hypothetical Kenyan-born Obama a citizen at birth without a naturalization process, and that would make Obama a NBC even if he was born in Kenya.
The circumstances of Cruxz's birth abroad to a citizen mother and alien father satisfy the statute in effect at the time Cruz was born.