That's obvious nonsense, since it would make a person's NBC status dependent on some other country's laws. Suppose Switzerland passed a law saying that all children of 100% Swiss ancestry born anywhere in the world are entitled to Swiss citizenship. Then you're saying that a child born in Ohio of American citizen parents of Swiss heritage is ineligible to be President? Ridiculous!
actually, that's British law. it's called 'British by descent'... which is why i'm able to pick up my UK passport if so desired
in order to insure their child is a natural born citizen, both parents would have to renounce any non-US citizenship and become US citizens before the child's birth.
otherwise the child would be a native born US citizen ... AND ... a Swiss citizen (using your example, tho i'm pretty sure the swiss don't see it that way)