I don't think it's particularly useful to see it as "serving a sentence," as in practice, we're dealing with an algorithm, which is dynamic and always current.
Its sense of "history" generally doesn't go back any further than its last data crawl, as far as I understand it.
The algorithm lives in the moment, even if its creators do not.
I agree with you, Glenn about Discover, HP.com, and linking.
The way I see it: If the niches are Heaven, then Discover is a purgatory and HP.com is Hell.
Neither Discover or HP.com will ever be high achievers because they're not designed to succeed with Google. That isn't their purpose.
Linking to either of those sites from the niches won't help the individual writer, just potentially cause problems for the niche.