In AEM 6.0, whenever the dam update asset workflow is run, an event is fired with the event.topic: "com/day/cq/workflow/event " and WorkFlowName as "DAM Update Asset". This can be seen in the event console(..system/console/events). But in 6.3, we don't see this event fired. A different event is fired instead with event.topic as "com/day/cq/dam" and type as "DAM_UPDATE_ASSET_WORKFLOW_COMPLETED". The same is not fired in 6.0.
In 6.3 transient workflow is introduced and update asset workflow is transient OOTB.
Standard workflows save runtime (history) information during their execution. You can also define a workflow model as Transient to avoid such history being persisted. This is used for performance tuning as it saves/avoids the time/resources used for persisting the information.
So the behavior is different in 6.3 than 6.0 and is expected.
DAM_UPDATE_ASSET_WORKFLOW_COMPLETED is internal event for Assets UI.
You can make workflow non-transient from workflow UI to get previous behavior.