If I create a dictionary entry for an activity and link use it in an IT-System the documentation is not shown on the main attributes. From what I read on your documentation, these two fields are supposed to be synchronized.
If you link an entry which does not fit the element (like, entry type activity with an IT-system) the documentation is not taken, this is a desired behavior.
KBA , BPI-SIG-PM-DIC , Dictionary for SAP Signavio Process Manager , How To
SAP Signavio Process Manager all versions ; Signavio Process Manager all versions