Can a reconstruction union be established even if the ratio of detached/multi-family houses exceeds 50%?

It is only for certain areas, but
I found a redevelopment zone in Seoul where the ratio of detached/multi-family houses is 55% based on the number of owners, and the union has already been established.
What is the case here? If the union is already established, it means they obtained more than 75% consent.
Aren't detached/multi-family house owners and commercial property owners always against redevelopment?