The Sun and Moon cycle should be enough to prove it in itself. The fact you cannot travel further across the sea in WW is because the King says it is too dangerous, hinting that there are mega Octos, or perhaps he simply doesn't wish Link to get sidetracked, and to save Zelda. And your fourth point is really irrelevant because that's to do with technology of the console, and not developer's wish.

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My BA Character: Agno Denstern
Thanks to Sugarpoultry for the fantastic signiature and avatar set!
[Symbols of the Interlopers?][The Minish Cap and Oracles Placement]