The top tier measures whether you are faking it
Premium adds mouse jiggler and clicker detection, irregular keyboard activity flags, an unusual activity report and video screen recording. Read together, those are not productivity features, they are integrity checks, and they only make sense if someone has a reason to doubt the person being measured. Stunda checks for machine-made input too, and says so: a block of movement that never interacts, or input at machine-regular intervals, is marked for review. The difference is what the finding is for. Stunda's annotates a record the tracked person can see, never deducts the time, and has no content or video behind it to scrub, because the tracker increments counters and discards the events. Time Doctor's feeds a case someone else builds about you.