I don't understand this idea that Penguin 1.0 just looked at the home page.
I agree with what atlrus said yesterday (I posted to the same effect last year): Penguin 1 was both page- and term-specific.
I have one specific internal (fourth-level) page that was obviously affected for its subject-term. It has a large number of unsolicited backlinks using the term as anchor-text, and I am as sure as I can be that this is the reason for its disappearance from Google SERPS. It was on Google page 1, and is still on page 1 of all other engines.