*Animation (NumberAnimation on y) with «duration: 0» updates the target property to «to» value.

*Animator (YAnimator) with «duration: 0» does nothing, the target property is not changed at all.

The documentation tells:

The value of the QML property will be updated after the animation has finished. The property is not updated while the animation is running.

But it does not work so when the animation duration is set to 0.

I agree that there is no reason to make an Animator with constant duration set to 0, but there could be a valid use-case with duration calculated at runtime.