Please note, that the spec edit has been mostly approved and finalized, but put on hold due to a major spec repo refactoring. But I don't think it should stop from shipping, since ideally it would be shipped together with CSSPseudoElement interface in M147.
Specific events are now extended to have `.pseudoTarget` that is either CSSPseudoElement (if interaction has been with pseudo-element) or null. This allows to have more specific information on the event origin, e.g. that not just an ultimate originating element (Event.target) has been clicked, but more specifically that it was ::after. Note that the Event.target is unchanged so event only has extra info on pseudo-element interaction. The events are UIEvent, AnimationEvent, TransitionEvent. mouseover, mouseout, mouseenter, mouseleave and their pointer* counterparts are not yet supported.