I think there may be a disconnect here (and I apologize if there isn't; this is not my wheelhouse)...

1. Some people talk about "land tax" meaning a tax on the value of _only_ the land. So you pay a tax based on the land, but not anything built on it.

2. Some people talk about "land tax" meaning a tax on the value of the property if you were to sell it; including any construction on it. This is the common situation in the US, to the best of my knowledge.

The former, taxing _only_ the land, is what (I believe) a lot of people are talking about when they say it will promote more/better construction on the existing land. Because you're paying the same tax regardless of what is built on it, so build whatever it the most useful for you.