@BlakeRichardson
The update command is limited to supervised devices by Apple, not us, sadly....
However, there is an alternative.... Using Systems Manager > Command Line allows you to do the same thing to multiple devices at the same time.
I don't have any of my Macs online currently, so can't show you exactly, but so long as they have the SM client installed, allows you to do a whole host of software update activities:
https://ss64.com/osx/softwareupdate.html
Furthermore, using the new (Under Organisation > Early Adopter) scripting capability, you can do this systematically as well.
In summary, there's several options available for you using SM beyond the MDM commands