If you want the coupler element to be created, you need to use the coupler tool.
End treatment is just information about how the end of the bar needs to be machined for the required coupler type. It is added automatically when placing the coupler or manually.
Another way would through some add-in or Dynamo scripts that would automatically add couplers at both ends. I don't have an example of this to recommend.
Ovidiu Paunescu, M.Sc. Str. Eng.
Sr. Product Owner | Autodesk Revit