This policy setting controls Outlook's "fast shutdown" behavior for add-ins. If you enable this policy setting, the BeginShutdown ...

This policy setting controls Outlook's "fast shutdown" behavior for add-ins.

If you enable this policy setting, the BeginShutdown and OnDisconnection events should always be called for all add-ins.  

If you disable or do not configure this policy setting, all Outlook addins should always use the Addin Fast Shutdown behavior and not have the BeginShutdown and OnDisconnection events called.