Does requiem have anything to do with the story?

[Shev]

So I was playing penumbra: requiem, because I just beat the last two, and I think I'm roughly near the end and so far it appears to have NOTHING to do with the game at all.

Spoiler below!

Aside from a few familiar voices, notes, and flashback images.

Without spoiling anything (or at least keep it to a minimum) does this game really have anything to do with anything?

[Yuhaney]

In the end of the game you can, and have to, decide how to end Phillip's story.
Also, there are some secrets in the game you might want to hunt down (nothing really story related though).