This is nothing new, anyone in the SEO world knows that this has been possible for years. It's not particularly long lasting as a strategy but it can be leveraged for things like link spam via massive amounts of cloaking sites.
This is the core of why Google uses things like links as a ranking signal. If they based it entirely on the content of the site, they're easily duped. While it's somewhat trivial to manipulate your backlink profile to increase your rankings, it's rather hard to fake links from known high quality sites like the New York Times for instance. So they can "trust" links more than they can trust the content of the site they're crawling.
So even though this site has a large amount of content indexed, the changes of it ranking for anything more than gibberish are so low that it doesn't even matter.