Yeah, which sounds like a fair guess, but the only way to know for sure is for it to be tested in courts, otherwise we're just guessing :) And as we probably all know, having large pockets for lawyers and lobbyists, makes a lot of what we think isn't possible, possible.
... other than "person x has never been and is not presently a citizen" this is as clear as it can get. Naturalized citizens are not eligible to be president, there is no gray space on this matter.
It's really not as crystal clear as you make it.