The last one can be useful but not for what the article describes. Windows has a set of system maintenance tasks that normally run every 3 days. These run during idle time so will not interfore with normal use. Idle time is defined as a period of 15 minutes with zero CPU usage and no user interaction. The command in question will run these tasks immediately.
Few desktop users will have a use for this command. But for laptop users this is a different story. Due to power management these systems will rarely be in an idle mode and the idle tasks may never run. The command will allow the user to manually start them.
The command does not terminate any idle tasks, nor does it free memory. By definition, idle tasks run during idle time and can not interfere with normal use. The command may require up to 15 minutes to complete and there will be no notification when done. Disk and CPU activity may be high so you do not want to do this prior to running an intensive task.