This OPC UA Property, of DataType BACnetEventState, is included in order to provide a way to determine whether this object has an active event state associated with it. If the object does not support event reporting then the value of this property shall be Normal. The BACnetEventState DataType is defined in 10.4.10.
While BACnet object types normally require the BACnet property Event_State, the OPC UA Object EventReporting is O. In absence of an event algorithm the property Event_State is defined by BACnet to be Normal. And therefore does not provide any valuable information and is not visible in this case.