Similar to Split model and Update Model Name on Occurrences and Delete unliked Occurrences using Model Name the Model Name set on systems will work as a filter when synchronizing Revit systems with dRofus systems. Without setting Model Name for Systems, the dRofus plug-in will not be able to e.g. delete obsolete systems in dRofus that are no longer present in the current model.
When using Model Name, make sure Model Name is utilized for all models for all disciplines that synchronize systems with dRofus.