Earlier quoted context omitted.
The theory goes that as those new rural communities develop the land value will begin to increase - which will in turn encourage densification to keep up. We see this historically in frontier towns that had absolutely no limits on sprawl (as land on the outskirts was available to anyone willing to stead it) but still had city centers develop and usually to the construction limits of the time.
"Encourage densification" is kind of bloodless, abstract language. How does this mechanism work in concrete terms? My understanding is that Georgism advocates raising taxes on people with property in desirable locations. They decide they can't afford the taxes, so they sell to a developer, who tears down the house and builds a bigger building. Another name for this process is "gentrification." The difference is that…
You have a 500m^2 plot of land. This plot pays $50k land value taxes. If one person lives on the land that person pays the full tax. If 10 people live on the property they each pay $5k taxes per year. If 50 live there then the tax is $1k.
Property taxes scale with the building so housing more people means higher taxes. That is being avoided by only taxing the land.
Alternatively, people hate taxes, they want to avoid paying taxes. If you want to avoid land value taxes, the only way to do that is to use less land more efficiently.