From man:

-m Monitor mode.

 Job control is enabled.  This option is on by default for interactive shells on systems that support it  (see  JOB  CONTROL  above).

 Background processes run in a separate process group and a line containing their exit status is printed upon their completion.
                  
                  
                  

from secure log:

Received disconnect from X.X.X.X: 0

Seems, if we set to -m, the exit status is prints on a current shell after completion of a background process which is exit 0. Able to witness in securelog.

From man:

-m Monitor mode.

Job control is enabled. This option is on by default for interactive shells on systems that support it (see JOB CONTROL above). Background processes run in a separate process group and a line containing their exit status is printed upon their completion.

from secure log:

Received disconnect from X.X.X.X: 0

Seems, if we set to -m, the exit status is prints on a current shell after completion of a background process which is exit 0. Able to witness in securelog.