So Github doesn't have managers, it just has Primary Responsible People, who sound an awful like they do the same thing? Just don't call them "managers", because you don't have those. Cute.
Every successful startup eventually discovers that the O(n^2) communication overhead of a perfectly flat org doesn't scale, and needs to adapt to deal with that. The question is whether to develop coordination specialists implicitly or explicitly. Developing doublespeak to protect an idealistic worldview from its incompatibility with reality does seem pathological.