Your probably right about that, I don't have any legal expertise. It seems that Article 15 states that each person has a right to a nationality, not to the nationality of the country they are in.
It's fairly common for children of illegal immigrants to be in such "gray areas" where they don't have any nationality.
One of my half-sisters was in such case, she was born in Austria but neither of her parents were Austrian, so she was ruled not to have the right for Austrian citizenship, fortunately Uruguay is not so strict and recognizes foreign-born children of Uruguayans as Uruguayan and finally gave her the nationality.
One of my half-sisters was in such case, she was born in Austria but neither of her parents were Austrian, so she was ruled not to have the right for Austrian citizenship, fortunately Uruguay is not so strict and recognizes foreign-born children of Uruguayans as Uruguayan and finally gave her the nationality.