WebLogic shutdown when work completes

If you go to Control-Shutdown-when work completes

status is SUSPENDING for 15 minutes...

so I do "force shutdown now" and shortly after WLS dies and status becomes FORCE_SHUTTING_DOWN.

With WLST you can do shutdown :

shutdown('${SERVER_NAME}','Server', ignoreSessions='true', timeOut=120, force='true')


Official doc:

http://docs.oracle.com/cd/E21764_01/web.1111/e13708/server_life.htm#START217



Why WLS doesn't exit the SUSPENDING status? My theory is that there are active threads for the FileAdapter and DbAdapter poller.
So how to do a graceful shutdown?
I would propose a WLST SUSPEND followed by a FORCE SHUTDOWN.