Basically yes. I used to write regularly for a large finance site. You've read articles from this site, they show up on HN regularly and its one of the top 100 sites in the world and bounces around in place among the top 3 finance sites.

Anyway, point is when I wrote for them, we had a list of places we could link to and places we couldn't. A lot of them where other sister sites the parent company owned. If we needed a source we first had to try to find it there. If it wasn't available there then there were another list of sites we were allowed to link to, which was basically top 100 sites.

Then there were sites we were NEVER allowed to link to. I remember one of those sites was Reddit. But there were many others. Then anything that fell in the middle was something we linked to if it was critical for the article, otherwise we wouldn't link at all.

So yes, its basically an SEO circle jerk at the top. Which is why you see the same 100 sites in all search results.