The problem is that the Petrel found an area around the torpedo tubes, specifically the catwalk area, leading from the after deckhouse to the tubes that appears to be there on the new imagery. So... either the Johnston sprouted all new torpedo tube mounts and deckhouses or the wreck that the Petrel found WAS NOT the Johnston.
The Johnston and Hoel were only separated by a few miles when they sank, and these were positions taken in the heat of battle, so they were subject to error. USNA work using Heerman's last reported position for Hoel places Johnston relatively close to Hoel's last reported position. Remember, Cmdr. Evans went off on his own, and Johnston's positions were sporadic and open to interpretation. We could be looking at two different wrecks relatively close together. We just don't know. Further surveys of the Johnston's wreck may glean more information. 'Til then, we just don't know quite what the Petrel found. A Fletcher? Certainly, but which one? The amount of debris, including the huge amount of debris from deckhouses, gun mounts, etc., indicates that it may, just may, have been the Hoel. With the absolute greatest of courtesy, match up the debris the Petrel found with what remains of of the Johnston. Watch the videos. You'll see what I mean.