MdmBarbarella, I did some testing and confirmed it is a forced shutdown, as you stated. It does look to Graceful first and then force if not successful. The next revision (3.4) looks to give a Graceful with Forced Shutdown and a Graceful without Forced Shutdown though.  Hope this helps.
I installed a few firmware updates on several servers (R730, R440, Windows 2019 LTSC) with the option "Update now". OME warns we:
Firmwareupdate causes cold reboot instead clean reboot of the operating system