The article means "track" in the sense of "uniquely identify the physical device," not "send location information." Uber had code that would persistently identify which device was being used across two different installations of the app, even if the device had been factory-reset. (I suppose they could do something like find the MAC address, although Apple has been making that harder.)

Furthermore, that code wasn't triggered, somehow, in devices near Cupertino, indicating that they were trying to hide the code from App Store reviwers.

I think I feel that this is very qualitatively different from gathering location data on users who have deleted the app (if such a thing were possible), but nevertheless a serious ethical lapse.