Hi - I’m the guilty party – glad you found it interesting, at least!
As @jeremy guessed, I scraped Kiwix’s Spanish Wikipedia up to a point in the interest of making a fully-static version for USB. Yes, it is lacking, but in the context of a searchable USB version, that was a necessity. I limited it to content that was within two levels of every category page I could find (manually compiled from the live Spanish Wikipedia). I used
wget for this against a locally hosted copy of Kiwix’s Wikipedia in Spanish.
The code for all this is not in github as it involves lots of manual steps and will probably confuse most people. I can put it up if you think you’d want to work with it, but it’s really not intended for public use and I can’t offer much support!