I see your rationale now. So link exchanges for long-long tails, makes sense.
I now see yours too.
My experiment was for 2 words phrases only. So anchor text patterns, might be the target of devalued links.
Some of mine are two words too, but my site is not chasing the news headlines, so I guess there are two types of link exchanges... the ones that want/need the "what's going on in the world this minute" type, and the ones that look for long term rankings for long-lived phrases.