No it is not this job that does this. The System_Defaults_System is only used for configuration, as mentioned above, the System_ProcessKeepClauses job will do the actual work. But as that is running every 15 minutes by default (look at job filter All Maintenance Jobs), there is nothing more you have to do.
Note that only jobs in an END (Completed, Killed, Unknown, Canceled, Error) state are removed. All other jobs (Waiting, Held, Console etc) will have to be set to an endstate first before they can be removed by the system.
Regards Gerben