[hananova]

Yes, but on a real stopwatch, or on a computer mouse, you can rest your finger on the button with almost but not quite enough force to actuate it, and activate it with a press.

On a touch screen you have to hover your finger over the button and move it down some indeterminate distance to actuate the button. The equivalent to the above example for a touch screen is to activate on release, as you can rest in a state “ready to click” just like on a physical button that way.

[IdiotSavage]

Interestingly the "activate on release" logic was implemented in computer GUIs long before touchscreens were common, used purely by mouse-click (a physical button).