Yes the stopwatch's buttons are different, but there is a reason for this. Imagine you are using a stopwatch. When the gun fires, you press the button with your finger. When the runner passes the finish line, you push the button with your finger. You will probably expect it to stop and start timing at these times, with no regard for how long your finger spends sitting on the screen, right? Now look at the buttons in other apps: they trigger when you release your finger, not when your finger touches the screen. This makes sense because you may be tentative about submitting a form, and it'd be scary if it just submitted the moment your finger grazed the screen, right?