It seems that all the new stuff, as of now, is under the “New Twitch API” section, which is small as Twitch seems to continue developing that API based on Trello (Roadmap). I imagine that once they have it further developed, that we may see something like before that we can pick the version of the API that we want to review from a drop down, but, given that it is still very much in it’s [apparent] infancy, it seems that is why it is organized like it is.
Just my perception of this, someone from Twitch would have to weigh in.