Here is some additional information about this behaviour.
Existing display Identification for WorkItem (WorkItemDisplayIdentificationDelegate) is being customized by implementing DisplayIdentificationDelegate interface which display process name + activity name as Display Identifier. And this is configured in service.properties.xconf file.
You can follow below steps for correcting display name on WorkItem page.
1. You can write you own delegate class which implementing DisplayIdentificationDelegate interface
2. Register your own custom class in service.properties.xconf file
<Option cardinality="duplicate" order="1" requestor="wt.workflow.work.WorkItem" serviceClass="ext.CustomWorkItemDisplayIdentificationDelegate"/>
Note- I replaced above existing serviceClass highlighted entry with my custom delegate class
3. You will have to modify above highlighted entry in service.properties.xconf file with the customized class which you wrote in step #1.
4. Propagate changes from service.properties.xconf file using below command. Execute this command from Windchill Shell.
xconfmanager -p
5. Stop Windchill Method Server
6. Clear Tomcat and Info*Engine cache
7. Restart Windchill Method Server
8. Observe display Identification for WorkItem
