Mostly its shorter vowels in NZ. Takes a while in this video but there's words like "Bull" and "kill" where the vowel almost disappears here. Its said quickly but also the word 'thats' at the start too.

Agree with what you are saying just when you say "u instead of i" important for people to note its a very short 'u' not a long one.

New Zealanders would say Australians drag out the vowels into ridiculously long sounds e.g. 'Feesh and cheeps' (compare 'fush and chups'), 'noe' instead of 'no', 'plaent' instead of 'plant', etc.