I think this page should be updated?
Personally I want to see bootstrap mode back. It takes care of the case where there are less than 30 posts. If it has to remain removed, there should be an adjustable threshold N that works like “the number of posts a tl0 user has to read to get tl1 is min(N, number_of_posts_in_forum)”.
Edit: That feels logically flawed, it should be a boolean option that when true (and the default should be true), the number of posts a tl0 user has to read to get tl1 changes to min(30, number_of_posts_in_forum) (that 30 is already adjustable I remember)