"The iPhone continues to store location data even when location services are disabled, contrary to Apple’s previous claims. The Wall Street Journal did independent testing on an iPhone and found that even after turning off location services, the device was still collecting information on nearby cell towers and Wi-Fi access points."2011: iPhone's Location-Data Collection Can't Be Turned Off - https://www.wired.com/2011/04/iphone-location-opt-out/
"Your iPhone tracks your location for a variety of reasons. It tracks you to calibrate sensors and to improve services, but also to show you ads."
2019: How to stop your iPhone from tracking your location - https://www.cnbc.com/2019/12/19/your-apple-iphone-tracks-whe...
2019: It’s the middle of the night. Do you know who your iPhone is talking to? - https://www.washingtonpost.com/technology/2019/05/28/its-mid...
"The best way to keep something secret is not to capture and store it in the first place. And that’s the crux of the privacy versus convenience debate now redefining our applications and software-based services ... Yes, maybe what happens on an iPhone stays on an iPhone, but some data should not be captured in the first place. Nothing more so than the significant invasiveness of Apple’s significant locations concept—a perfect illustration of just because you can, doesn’t mean you should. This is a continually building data repository of the locations you visit, along with times and dates, detailed maps, even the mode of transport to get you there and how long it took."
2020: Why You Should Stop This ‘Hidden’ Location Tracking On Your iPhone - https://www.forbes.com/sites/zakdoffman/2020/10/04/apple-iph...
“Both iOS and Google Android transmit telemetry, despite the user explicitly opting out of this,” wrote researcher Douglas Leith from Trinity College in Ireland, in a recently published academic report ... “To date, Apple have responded only with silence (we sent three emails to Apple’s director of user privacy, who declined even to acknowledge receipt of an email,” Leith wrote. Since then, Apple has made public statements critical of Leith’s research and insisting privacy and opt-out measures do exist.
2021: Apple, Google Both Track Mobile Telemetry Data, Despite Users Opting Out - https://threatpost.com/google-apple-track-mobile-opting-out/...
"And there’s also a more fundamental issue with this technology. Its euphemistic description as a “crowdsourced” way to recover lost items belies the reality of how these items are tracked. What you won’t find highlighted in the polished marketing statements is the fact that AirTags can only work by tapping into an Apple-operated surveillance network in which millions of us are unwitting participants."
2021: Remember, Apple AirTags and ‘Find My’ app only work because of a vast, largely covert tracking network - https://theconversation.com/remember-apple-airtags-and-find-...
------
As for "anonymising" user data, Apple has enough data points on its users from various services and sources it collects its user data from to make it meaningless.