It was because the vaccine rollouts focused more on regions and age ranges that favoured NZ-europeans (Pakeha), either intentionally or not.

Yes it was intentional, afterall it makes sense to vaccinate the older people first, and white people just stopped having as many babies so disproportionally a lot more older white people exist and far fewer younger ones. Younger demographics tend to be full of minorities, such as Maori.
Likewise it also makes sense to vaccinate people in urban areas first, i.e. regions where the virus actually spreads very quickly. It makes zero sense to vaccinate some rural isolated village first where the virus may not even spread at all. And as a matter of fact, Maori tend to live in rural areas, white people in more urban ones.

Phrasing it like that, intentionally or not, creates the impression of malice, systemic racism or conspiratorial thinking, ranging from racist genocide to covid-q-anon type theories. When the actual answer is that it makes sense to vaccinate the most vulnerable people first, i.e. older people & those in urban areas.

But they don't need that, they bloody won a war against the British at a time where they were still one of the biggest powers in the world, and basically forced the British to sign a treaty.

Well that's just not true.

The british won. That's why New Zealand was a british colony, why white people are the majority and maori a minority.
The Treaty of Waitangi was signed because that's how Europeans got colonies in the first place, protection treaties/unequal treaties. Almost every single European colony in the 19th century was established through a treaty and the Europeans build upon that to encroach and gain more influence and power in a region.
The Treaty was also signed BEFORE the wars. First New Zealand became a colony, then the British bought land, then several years later minor Maori resistance against their colonial overlord started and 1 more decade later the Maori actually fought in a united front against the british, but they still lost. About double the amount of Maori died than British, and the casualties are still very low : \~2000 dead Maoris, \~800 dead British.