Earlier quoted context omitted.
The idea is that you tax the land only as if it was being used for best use - so that every property is encouraged to develop to maximum density. I suspect that in actual use it would end up having a small to no effect.
In actual use it would, in most cases, ensure that people would not, could not have long-term ownership of land passed down from generation to generation. There would be significant social downstream effects & likely upheaval caused by this, & that would be compounded by the deleterious results of forcing more & more people to live shoulder to shoulder in the name of that maximum density you mention. No system of tax…
Having un-utilized land in your family generation after generation codes as noble, but economically this is much worse than owning an AirBnb or a vacation home or being a Chinese investor who collects vacant luxury condos, or any of the other boogeymen of housing discourse. These people hold one unit off the market, and in the meantime they maintain it or finance its construction. The landowner builds and holds wealth for nothing but parasitism.