It's true that Google does recommend "optimization", even for their in-house content producers. However, some actions that webmasters call optimization are seen as "manipulation" and they get algo slapped. I believe the difference often lies in an overall website historical picture, coupled with a current total profile that folds in a couple hundred factors.
This isn't the Infoseek era anymore, but a lot of so-called SEO information still has its grounding back in those days. It's risky to think of Google ranking as something you can easily and regularly play around with through mere technical changes.