[css-animation-events] Initially paused animations emit animationstart events

The spec does not forbid animationstart event to fire on an element whose animation-play-state CSS-property is set to paused, which is counterintuitive:

Is this an omission or a deliberate decision?

I believe it's a deliberate decision. If the animation has entered its active interval, it is (potentially) affecting the target element's style so the event should be dispatched.