Looks like the extra section isn't operating today. Given how portions of JFK are still flooded and damage assessment has only just begun, it may be another day or so until the airport opens back up.
An airbus, according to Hawaiianair.com seems to be scheduled actually, though the 767 could indeed operate the flight nonstop if necessary. The stop in JFK is likely for crewing reasons.
The stop may also be because of possible fuel contamination or issues with the fuel pumping system at JFK (unconfirmed as of now, but still a possibility). If so, then the best option is indeed stopping for fuel at LAX...the eastbound fuel stop to fill up the tanks so they have enough fuel to fly roundtrip LAX-JFK-LAX (so no need to fill up at JFK). Westbound fuel stop to top off for the rest of the flight home.
Of course, you can substitute LAX for any other intermediate airport on the mainland, but just going with that based on the info HA released yesterday.