[System.Diagnostics.Conditional(Strings.Assertions)]
public static void AssertNotEndEvent(StringReference name)

In order to minimise the performance cost of End Events when there isn't one, the Animancer.AnimancerEvent.Dispatcher won't even check the end time when there is no Animancer.AnimancerEvent.Sequence.OnEnd callback.

That means if a callback was bound to the Animancer.AnimancerEvent.EndEventName it would be triggered by any state with an Animancer.AnimancerEvent.Sequence.OnEnd callback, but not by states without one. That would be very counterintuitive so it isn't allowed.