As for the "Load Optimized Defaults" reason , see :
https://forum-en.msi.com/index.php?topic=100566.msg732929;topicseen#msg732929
/py means program main bios block
/sn means do not make a backup of old bios to floppy
/wb means update the bios boot block
/cd means clear DMI-data hw pool
/cc means clear cmos (doesn't always work so you always have to clear with jumper after flash)
/ld means destroy existing checksum in onboard cmos , giving the load of new values a fresh start and proper load.
/e means return to dos prompt after flash (gives the possibility to rerun the flash if something goes wrong)
Only this will give a clean flash with all updated and a clean motherboad/cmos like iif the board was newly delivered from factory with the new bios version.