I'm not sure what your point is here.
The writers said that the show will focus only on the mysteries that affect the main characters. Yet, this episode has no apparent effect. Maybe it will, but I'm getting a vibe of 'producers say one thing, yet do another', which they have a fairly consistent history of doing.
I don't think they were only referring to the main characters, but to characters in general.
This episode was about revealing more of the lives of Jacob and his brother, and how they ultimately arrived at the places they did. One as the "protector" of the island (who is then required to find candidates to replace him), and one as the Smoke Monster which desperately wants to get off it.
Frankly I don't see how it could be any MORE integral or relevant to the story going on now. Plus it was nice to get a better explanation of who these characters were, and how their life-long battle of wills got started.