what are you trying to do related to Update Manager? VUM is used for ESX(i) patches and upgrades as well as virtual hardware and VMware Tools upgrades. I don't know what you would want to trigger where VUM would be useful in alarm actions.
I'm digging around trying to see if there are any configurable alarms or triggers, like performing an automated VUM scan when new patches are released or automating some of the VUM management using PowerCLI. I can't find any configurable alarms but after reading the item I previously quoted, failed to find any place where this exists in vCenter, hence the question. I'm not sure what triggers I would like to use, but as the feature doesn't appear to exist, the question is moot anyay! I'm still puzzled why the documentation refers to this feature though!