I really don't see how you can read it that way. (I'm not even sure what "born citizens whose citizenship would be in doubt" means.) But I've been reading birther legal analysis for a couple of years now, and it usually leaves me thinking "how can anyone read it that way?" so there's probably no point in pursuing it further right now.
What's so hard to understand?? Minor said "Some authorities" go further and declares as citizens children born in the country WITHOUT regard to the citizenship of the parents. This group of citizens might include NBCs, but for those who aren't, there is doubt about their citizenship. It doesn't say "some authorities" declare these persons to be natural born citizens, just citizens. For that class of citizen there is doubt, but some that can be resolved, some that can't.