If the animation is so slow that it is still visible after your finger isn't obscuring the button anymore, I'd argue it has to be really slow and is not snappy anymore. It also doesn't behave like anything physical, because physical buttons/sliders only move while you're touching them.
The gold standard used to be to make buttons large enough so they are never fully obscured (for toggles, the label can be included to be part of the button) and to highlight them when pressed and remove the highlight when released. (Like keys on a virtual keyboard mostly still behave.) That way, you have a clear indication of when you press something, and it coincides with what your finger is doing, and doesn’t lag behind.
The gold standard used to be to make buttons large enough so they are never fully obscured (for toggles, the label can be included to be part of the button) and to highlight them when pressed and remove the highlight when released. (Like keys on a virtual keyboard mostly still behave.) That way, you have a clear indication of when you press something, and it coincides with what your finger is doing, and doesn’t lag behind.