While I agree that too many people argue about immersion incorrectly, i do not agree with the OP when saying they say that certain aspects of the game are immersion. When you think about a game world its not the UI that immerses you its the actual game play, sure UI can be part of gameplay, but once you get over how to use the UI its pretty much behind you in immersion. Immersion is subjective, how can one say "that's part of the game, it IS immersion" when to another its just a bit of coding (programming).