So reading your first post where you say he wants to relocate "because he’s had a job offer and he’s increasingly concerned about the threat of war" - and this post where you say he's wanted to visit for ages - I think you would be unreasonable to dismiss it out of hand.
My (English) brother emigrated about 18 years ago with his (Kiwi born) wife - driven largely by better quality of life in NZ, money going further for buying a property (they lived in London) and wanting a good upbringing for their toddler son.
Some 18 years on, my brother (and his wife) both remain very happy with his decision and my brother is terribly proud he now has NZ citizenship (and sent me the video clip of the ceremony).
There was some culture shock for him at the beginning - namely, the lack of multiculturalism (and lack of diverse ethnic food stuffs - he's a bit of a foodie) and 'newness of New Zealand. But then he was initially comparing Auckland with London.
The principle disadvantage for him after 15 years or so was not being able to spend time with our ageing mother with her at end life because of imited flights and their expense from NZ to UK during pandemic. (That said, other than myself, my other sub,Ines and mother's friends were not permitted to visit my mother due to Covid restrictions - so his returning to UK wouldn't have made a difference).
So I would say don’t dismiss it out of hand! Discuss further, explore your concerns and his motivations, the practicalities and whether a compromise is possible - eg a three year trial period and a plan to return. Plus pre booking a certain number of return visits.
Whilst don't agree Europe is under threat by those pesky Ruskies, I do think that more generally NZ is safer than the UK.
EDITED to say sorry for typos - but you should get the drift