From the article, explained: At the time, Uber was dealing with widespread account fraud in places like China, where tricksters bought stolen iPhones that were erased of their memory and resold. Some Uber drivers there would then create dozens of fake email addresses to sign up for new Uber rider accounts attached to each phone, and request rides from those phones, which they would then accept. Since Uber was handing…
To halt the activity, Uber engineers assigned a persistent identity to iPhones with a small piece of code, a practice called “fingerprinting.” Uber could then identify an iPhone and prevent itself from being fooled even after the device was erased of its contents.
I also interpreted "track" as "report geolocation data," but that's not what the reporter means, and honestly the reporter's meaning is more consistent with, e.g., "this website is tracking users" or "Do-Not-Track".