Not to mention this is the way that physical buttons work in the real world. People would be immensely annoyed if suddenly doorbells, elevators, light switches, etc. didn't operate until release.
I think the difference is that you can touch physical buttons without activating them, making it a two step process analogous to activation on release on touch screens.
Physical buttons use edge and level triggering, and depending on the system either leading or trailing edge triggering. They don't universally use leading edge triggering.
