Plugin failed to startup (disabled), yet it's event listener is receiving events anyway

This is strange. One of our Jira instances (Data Center) was restarted and a custom add-on did not startup, yet it’s logs show that the event listener in the add-on is receiving events. I don’t know how that can happen if the add-on has not actually started-up.

Here’s the event listener:

public class IssueEventListener implements InitializingBean, DisposableBean, LifecycleAware {
   public void onIssueEvent(IssueEvent issueEvent) {
		System.out.println("Event recieved: " + issueEvent);

    public void onStart() {

The log shows that the add-on is disabled for some reason, but that’s besides the point. We expect that when the add-on is disabled, then any listeners that it defines should not be receiving events.

Is this a bug or am I misunderstanding something?