It is poorly worded but I think effectively it's true. If I understand correctly a 10000 sq ft lot would be taxed the same regardless if it was a 1 story house or a 6 story condo... So effectively it's a discount compared to the way normal property tax is levied that values the cost of the structure on the land... https://en.m.wikipedia.org/wiki/Land_value_tax

Well, yes. Though this interpretation only makes sense if "urban buildings" doesn't mean "buildings in an urban area" as most would expect, but instead "high occupancy buildings". It is either wrong or very poorly worded.

It creates the incentives for creating more housing, in that land is most likely to be brought into efficient use.

It won't create more square-footage of land in which people can live, but it makes it more likely that cities will grow in ways to sustain more people.