It's Not Me, It's You
Nothing new, people will do very distasteful things to track you
That said, it's in a state I feel you can confirm the script works as advertised: it tracks the user on the site, and it sends performance data as per the above information.
What really bothers me is that this messy and arcane language (how many of you JS "fans" know how it works under the hood, or how to guarantee formally anything written in it?) is silently run on every webpage there is. You load an innocuous kitten laden website, and a ton of invisible code is run to track, exploit, or mislead you. Fan-ta-stic.