alt Hacker NewsNo, even for stopwatch, trigger on release is the correct choice, as it’s more precise.
When tapping, I have to see, or in case of watching for some event to happen to stop the time, feel/guess when exactly the distance between screen and finger approaches zero. With a stop button triggered by release however, I can just calmly rest my finger on it and raise when the event happens, without any guesswork.
How does a real stopwatch work? Hint: it starts/stops on press, not release. So that's what the app should do, to map with prior expectations.
"Nobody uses real stopwatches anymore" might be somewhat true, but in athletics training they still do, and it just shows that it's not possible to adequately reproduce a thing on a touch screen and have it be as functional as the real item. A stopwatch app on a phone will always be a poor substitute for a real stopwatch.