Patch 4.10 - Development Updates by Daidalos Team

[Avimimus]

There is a difference between field of view (number of degrees encompassed in the image) and field of view (number of degrees not obscured by the cockpit). Il-2 actually lets one distort the image so as to see more degrees than a screen's width alone would allow.

I'm guessing that what you're most likely seeing with the Pacific theatre aircraft are simply better cockpit designs intended for visibility during carrier landings.