It's the second Konami game to receive a downunder delay in a month, after Castlevania: Lords of Shadow 2 was pushed back by a week in Australia and New Zealand. As NZGamer notes, the downloadable versions of Lords of Shadow 2 weren't affected by what was then a "shipping delay," and while it's not confirmed there's the possibility the same may apply to Ground Zeroes.
In other Ground Zeroes news, series creator Hideo Kojima explained this morning the game doesn't feature a Platinum trophy on PS4 because of Sony regulations. Speaking on Twitter, Kojima said, "They won't allow us to have them for [a] non-full price game."
Metal Gear Solid 5: Ground Zeroes (3/6/14)