Part of it is simply fog of war, coupled with some censorship in the theater of battle.
For example, the US believes that the Haruna has been sunk. However, she is not even near the Philippines. A cruiser was damaged but not sunk in that attack.
There will be a lot of confusion and incorrect claims until the end of the war. When the allies got a look at enemy records and were able to compare them with our own, then the battle claims in many US records were adjusted.
Yes, after the war there will be a considerable adjustment of reports. In the Pacific, the United States will create the Joint Army-Navy Assessment Committee (JANAC) which will compare available Japanese records of shipping losses to American reports of the same losses.
A number of submarines with outstanding war records will see their official claims adjusted, generally downward. A number of officially reported attacks and kills will not be borne out by Japanese records, and in most cases, even where the Japanese confirmed loss of a ship, the tonnage will be reduced.
However, despite JANAC’s adjustments, it will be clear that the “Silent Service” slaughtered Japanese merchant shipping, and accounted for a significant number of combatants as well. What Doenitz tried, and failed to do against the British, the Americans will accomplish against the Japanese.