No, "dense housing" is code for multistory buildings in a mixed-use neighborhood (like you already find in many parts of the city!). It doesn't matter very much whether those apartments are 30 or 200m^2, the density is several times better than in a neighborhood of single family homes as you find them just a few km outside of Berlin's city center.

Japan style housing, just like British, is "dense" in the sense of buildings being physically close. It's not what the post is about - it's about building buildings with higher number of storeys.