"At common law, with the nomenclature of which the framers of the Constitution were familiar, it was never doubted that all children, born in a country of [p680] parents who were its citizens, became themselves, upon their birth, citizens also. These were natives, or natural-born citizens, as distinguished from aliens or foreigners. Some authorities go further, and include as citizens children born within the jurisdiction, without reference to the citizenship of their parents. As to this class, there have been doubts, but never as to the first. For the purposes of this case, it is not necessary to solve these doubts."
You need to read more closely. It says there are DOUBTS about anything BUT children born of parents who are citizens. Keep in mind, this was AFTER the ratification of the 14th amendment. If the only thing that mattered was jus soli birth, the 14th amendment would have made it so and there would be no doubts about children born 'without reference to the citizenship of their parents.' But they don't say that. The only citizens who are natural born without any doubts are those born in the country of parents who are citizens.
And again, the WKA decision specifically mentions that they determined the citizenship of a child whose parents are permanent residents. The parents status mattered.