Such a comment shows why there is so much confusion about this. There are ONLY two ways to be a US citizen: one is NATURALIZED or one is NATURAL BORN. That is it. Nothing else grants citizenship.
It is not even clear that he is a citizen at all. He was NOT naturalized so if not natural born then he is NOT even a citizen.
One can be a citizen at birth, under the statutes, and not be natural born. One can also be a citizen at birth under the 14th amendment, and still not be natural born.
You do know that the constitution doesn't define "naturalization" either? That does not however mean that Congress is free to change that definition, although they have. The funny thing is, they did it under the very power they were granted to define an uniform rule of naturalization.