Is Japan really what unusual? From what I hear the building codes are uniform so the spec for high density housing is similar to that of a single family home.

If builders in Canada have to build high density housing to a more costly specification then it’s justified that they won’t find it cost effective even if given the chance to do so.

In effect, the low cost of Japanese housing could be from both the zoning code and the building code. (As for culture, those two affect culture and are affected by culture so it’s hard to distinguish.)