Since he didn't need the extra fuel to reach friendly territory, I would think failing to drop tanks the moment a pilot realized combat was imminent suggests he believed himself good enough and/or in advantageous enough of a position that he could take the opponent and still have plenty of fuel remaining for more hunting. And that's how I always read the account, as a hunting trip.
http://en.wikipedia.org/wiki/Thomas_McGuire
McGuire according to the wiki entry had told the pilots in his group to keep their tanks so they could complete their mission.
McGuire’s altitude was roughly 300’ AGL when he went into the turn. No margin of error at that height. Plus from the wiki entry it seems that McGuire’s ambition may have gotten the better of him:-(
McGuire’s running mate and competitor Maj. Richard Bong will show up in the NY Times in about 7 months, regrettably.
Regards
alfa6 ;>}