I agree. It was about building the structure of a social network around the "asymmetric follow," and doing it in a way that facilitated the curated transitivity that Chris talks about.
What was the social network with public relations between people that failed because the "follow" was symmetric?
This is a common statement that benefits from explicit context: Twitter's innovation specifically was importing the "asymmetric follow" into a social network, a graph in which nodes represent individual people and in which relations are generally public.