Can you share the law or reference that states such? AFAIK, citizenship did NOT require both parents to be citizens, birth on US soil alone was enough. If you were born overseas, either both parents were US citizens OR one was a US citizen with at least 5 years adult residency within the US.
Don’t confuse “citizen” with “Natural born citizen”, although the NBC part has always been a little difficult to define. If he was born overseas though, with Ann being his only US parent, he wouldn’t even be a citizen. If he later became one, he would be a “naturalized” citizen. This is why it’s so important to verify he was in fact born in Hawaii. Because of the laws at the time (US Citizen parent must have been in country 10 years, five of which over the age of 14 or 16-depending on the source and doesn’t matter because she was 18), WHERE he was born is the most important factor.