> I checked this by manually disabling and enabling tracking option for the Stack app and comparing requests in both cases.
> And that's the only difference between allowing and disallowing tracking
This is revealing! I'd wondered about Apple's curious wording "Ask App not to track" leaves suspicious wriggle room - apps may not track by an id, but could easily 'fingerprint' users (given how much other data is sent), so even without a unique ID, enough data would be provided for them to know who you are 99% of the time.
Amended Dead Privacy Theory:
The Dead Internet Theory says most activity on the internet is by bots [0]. The Dead Privacy Theory says approximately all private data is not private; but rather is accessible on whim by any data scientist, SWE, analyst, or db admin with access to the database, and third parties.