Team Services now allows work item states to be customized and you can change the workflow to your preference. This is explained in the previous post “Custom States for Work Items in Team Services with New Process Customization Experience” in detail. As explained there you can hide available default states and use your custom sates instead of them. But as of now state change from a custom state to Completed category state does not update the Closed Date and Closed By fields in Bug and User Story/PBI work items. For Task work item in custom state , changing to Completed category state, updates Closed Date but not the Closed By field.
Let’s further understand this issue with an example.