Mail template workflowDocuments variable is not evaluated in task mail notification

1. In Studio the following variables are described to be working (see CONFIGURATION / Templates / Mail Templates) :

   - In the context of configuring a notification to be sent when a task is assigned during a workflow
   
   
   ${recipients} 
   ${userUrl} 
   ${docMainFileUrl}
   ${docState}
   ${documentLifeCycle}
   ${docTitle} 
   ${docUrl}
   ${docId}
   ${taskInstance}
   
   Also, the following workflow related bindings are available:
   
   ${workflowStartTime}
   ${workflowInitiator}
   ${WorkflowVariables}
   ${NodeVariables} 
   ${workflowDocuments}
   ${nodeId}
   ${button}
   ${nodeState}
   ${state}
   ${nodeStartTime}
   ${nodeEndTime}
   ${nodeLastActor}
   

2. when using a template like the following :

   hello this is a test mail!!!
   
   hop -> ZZ ${workflowDocuments[0].dublincore.title} ZZ
   

   in a worklow (see Mail notification in the General tab of a task).

3. the document title is not processed resulting in

   hello this is a test mail!!! hop -> ZZ ZZ
   

4. after testing further this works fine in 7.10 with latest HF and does not work any longer in 8.10 (with HF or fresh) and later versions. So, something has been broken between 7.10 and 8.10.

Note: see comments for further testing