Yes that is the animation glitch in the beginning of iOS 10. The animation did start instantly but had a little hiccup. The button was and has been responding instantly when you push it all the way though iOS 10
until iOS 11.
There isn't a hesitation in the animation in iOS 11. It's simply that
nothing is happing for a half second or so and then the animation begins after pressing the button. It's a change in timing with the capacitive buttons on the 7, 7plus and now looks like the 8 in iOS 11. It makes the phone feel slower.
[doublepost=1506097141][/doublepost]
Somebody already posted this but it shows best what we are describing. Notice how the 10.3.3 phone begins the animation to close the app instantly whereas the iOS 11 device is always slightly behind closing.