Years ago I used such a map to travel to a few faraway places with a similar climate to discover ecosystems that felt close to my own and yet so weirdly different. A bit like an uncanny valley without the revulsion because it was a beautiful experience.
I would have used that map a different way: Find close locations (to save on transportation cost, time and footprint) with a radically different climate (for the change of scenery etc).
The title reminded me of Dwellers in the Land, the Bioregional vision by Kirkpatrick Sale. Politically as unfeasible an idea as any wide-eyed utopia, yet very much central to any realistic hope of sustainable, long-term survival.
Yes it lost a lot of integrity for me when it shows New Zealand as having one single ecological system (bioregion) - a country arguably as biodiverse as the entire USA which it shows having at least 18 bioregions. Disappointing.
An excellent explanation can be found in a video[0] which also relies on the "Marine Ecoregions of the World" by Spalding referenced in the OP article.
0. https://www.oneearth.org/navigator/?view=bioregions