Yeah... it's complicated. :)

(As far as I know) there were no restrictions on anyone who was Māori or part-Māori (which would have been a fair few people) from serving in the NZ Army by 1939 (and there were certainly Māori veterans of WWI). Some Māori politicians and community leaders however wanted to raise the profile of Māori as subjects of the British Empire and pushed the NZ Government to create a dedicated Māori Battalion. (The 28th.) Initially many of the officers were European, (though the first 2ic of the 28th was a part-Māori WWI veteran), but these were replaced over time as Māori officers gained experience.

The 28th initially shipped out with the 2nd Echelon of the 2NZEF (the 5th Brigade) and was involved in anti-invasion duties in the UK, but once the brigade was reunited with the rest of the Division in Egypt the 28th became an additional battalion that could be moved between the Division's three brigades to provide extra infantry oomph where it was needed, and ended up fighting in Greece, Crete, North Africa, and Italy - receiving more individual bravery decorations than any of the other NZ battalions. (One private even won a US Silver Star.) :)

The difference (I guess) is that the unit wasn't there to keep "them" separate (and "in their place"), but rather at the insistence of Māori leaders to provide a opportunity to "prove the worth of Maoridom...and even secure the long-term goal of Maori autonomy". (NZ Historian Claudia Orange).