I think I found a conversation about it at GameFAQs. They're talking about SH1 but it sounds like it's the same thing.
Sounds like it will make the view be fixed in the aim mode, from right behind your shoulder. You would be able to see enemies in front of you better, but the view would be more limited. And if Patman is right, then you could still switch to the regular view by hitting the aim button.
http://www.gamefaqs.com/boards/198641-s ... l/48752124It seems like something you could easily change and try out mid-game.