As I take it from the ad campaign for the other film in this pair, the American government used a ginned up photo op (which is a lie, while it was not the first flag, it was not a staged shot) to create an image by which America could rally around the troops and win the war (the ad campaign made specific reference to how wars are won or lost on a single image).
FReepers have complained about the focus on the Iwo Jima soldiers lives at home. Again where they are portrayed to be pawns and wrongly extrapolated by Mr. Eastwood and the critics to be "the only guys who mattered". No one in their right minds ever made that claim except for liberals (and Mr. Eastwood has gone soft) looking for an argument on which to make a case against the imagery of war.
Within the articles on the first film, you will find questions of whether we were justified in fighting the battle and if we behaved in an improper manner.
This is why these same questions must be asked not only of the Japanese Emperor and Military Commander, but also of the soldiers in the field.
So omitting details of warcrimes is significant.
I can understand it more from a ratings standpoint. I'm expecting it to have some bloody battle scenes. A graphic gential mutilation scene might send it passed R territory. But who knows what the ratings board will allow, they are about the dumbest bunch of people allowed to meet together.