I know you couldn't find it, but what was even the basic principle? It's hard for me to imagine that dramatically increasing land use, transportation and infrastructure costs could be environmentally beneficial.
EDIT: found it https://www.nature.com/articles/s41598-021-01477-y
The actual study is filled with it’s own problems such as ignoring land covered by water etc, but that’s largely irrelevant here. However the real issue is it’s looking at land use around cities which are rarely independent. The area around London for example isn’t a single city it’s a cluster of different cities of various densities that all bleed into each other. Is to use a US example is Patterson part of NYC? How about Stamford and or Newark? If not where exactly do you place the borders between each of them?
Looking at population in the heart of NYC vs the surrounding areas over time and they are fairly independent.