Whilst different places had different rules (or interpretations of the rules), the app wasn’t actually required to frequent most places that I went to. What it did mean was that if you showed you have checked in on the app then you weren’t required to register manually at the venue, by leaving contact details for example.
In practice, most people used the app because if you weren’t going to use it due to privacy concerns then you probably didn’t want to leave your name and number either. Whichever way you were doing it, Boris would still receive the instant notification to tell him that you were having a pint.
As for tracking your location, it has never done that. It keeps a record of your check ins for 21 days (on your phone so, for example, when I changed my phone it lost my checkin history for the previous weeks). It also keeps a record of contacts (secure I ds of people I have been in contact with). If you are tested positive then you have to give permission for those people to be notified.
If you don’t specifically check in then it doesn’t know where you have been.
People have claimed that it is doing stuff it shouldn’t behind the scenes, but with the usual lack of evidence.