The question is simple - how can I install updates listed as "optional" in Windows Update using the Cluster-Aware Updating feature in Windows Server Failover Cluster?
I installed all the important updates and now the plug-ins say there are no updates left, but if you use Windows Update you can clearly see there are some.
EDIT: I found out that I need to provide the parameter BrowseOnly with the value True (or 1). I tried it and the CAU Microsoft.WindowsUpdatePlugin returns error that the argument value is invalid.