Fleetsmith currently handle Supplemental updates (i.e. updates which Apple will occasionally release outside of the standard version release cycle, e.g. not an update from 10.4.2 to 10.4.3) by notifying the user, provided the below setting is checked:
This setting is found in Apps and Settings -> Automatic Updates - macOS -> Configure.
Note that at this time, Fleetsmith cannot force this update (meaning that we can't require the device to install it) but this option will show users a notification (through macOS) that it is available as below: