It's possible to do a warm reboot into a new kernel without ever powering down and re-initializing RAM. Also, it may not even be fully rebooting, but instead d

It's possible to do a warm reboot into a new kernel without ever powering down and re-initializing RAM. Also, it may not even be fully rebooting, but instead doing something like killing all processes except init (launchd) which then starts up the installer. I haven't run it, so I don't know exactly what it's doing, but there are several ways to "reboot" without fully rebooting.