I don't know, maybe they are still vaccinating their risk groups, so it makes sense. But at one point in future they will have to open the borders and accept the inevitable.
We are aware that after preventing people from mixing, our immune systems are now more at risk from more typical virus outbreaks this wintertime, which is one of the costs of lockdowns.
We have already seen in history how isolated populations can be at risk of viruses such as smallpox. New Zealand's attempt to isolate the world is making the best out of a bad situation, but it's by no means the only way to "trust the science".
It's kind of silly to look at it out of context. Look at those Kiwis they locked down over 1 case... Because theres been 6 months without any cases so its easier to lock down and stop the spread of that 1.