What if you fly this person (who is great on paper) to Wellington, and they turn out to be the most toxic person you've ever met. What if your luck is truly awful and you fly out 100 of these people?
Yes, we've all met (or been, at occasion) such people; and yes, it's theoretically possible to interview 100 of such people at the same time. But in reality, the probability of that happening is astronomically lower compared to the probability that the problem was in the interviewer in the first place.
The costs of this interview are higher but then so is the relative gain of a good hire if they're bleeding talent internationally. The fundamental nature of the gamble is the same.