JFK may be a moderate sized airport, but I don't think a hurricane has a pressure differential of .02" in the area equal to JFK. Their altimeters should read the same. But, as what seems to be usual for anything at JFK, LGA, or the NYC metro airspace, they don't live to the same standards as the rest of the country. They get to make up their own rules quite frequently.
Also, the difference between 29.77 and 29.79 would be 20 feet, not 52.