If they left out parts of the pacific ocean that is irrelevant to the game, I can't see a problem. Only realism fetishists would be annoyed about not having vast stretchces of empty ocean to paddle around in.
In Silent Hunter III I've heard about people who navigated all the way to south africa and so forth. Me, I stuck to my convoy routes and paid USA a visit. To me, they could have left out most of the atlantic south of equator and I wouldn't have noticed
