Nobody cares if matplotlib is outdated. It served its purpose here, which was to show how plotting data can lead to further understanding data. You don't need a fully featured tool to do so.
> Each one of these needs to be scored (well, sorta - there are various tricks you can use to avoid scoring some docs, which again I'm not at liberty to discuss)
I suspect they do indeed use such URLs to track which link the user clicks. It's not that they log the IP with the click, but rather, the click allows implicit relevance feedback with respect to the issued query. This can be used for machine learning (to improve ranking, for example).