I am having issues with the accuracy of live arrivals/countdown information. I happen to live literally adjacent to a tram stop (Wandle Park) and can sit here with the official TfL trams countdown web app showing trams that are due (https://tfl.gov.uk/maps/track?Input=Wandle+Park+Tram+Stop&InputGeolocation=51.373403%2C-0.113282).
My observations show that the data is inaccurate to around five minutes, whereas the platform displays are accurate to within 1 minute.
Why is there disparity between the platform displays and the API data? Is the API data simply an estimate based on the timetable?