Definitely not recommended -- a REBOOT /S is run inside TCC, not TCMD, and results in everything else in your system being (abruptly) shut down. This means that TCMD will not get a chance to save its settings.
How is one to safely shutdown the system? The documentation for reboot says:
<table style="line-height: normal;" border="0" cellpadding="0" cellspacing="0"> <tbody> <tr style="vertical-align: baseline;" valign="baseline"> <td width="48">
/S</td> <td>Shut down the system, but do not reboot. This is equivalent to selecting Shutdown from the Start menu, then selecting "Shut down the computer" in the shutdown dialog.</td></tr></tbody></table>The start menu about the only other way I know to safely shutdown and the /s is supposed to be the equivalent