It's not a jBPM5 engine issue.. I mean you have the tooling and the engine. The engine works and it's difficult to sync the tooling and keep it updated. Right now there is a brilliant team working on it and you will notice that there is a standard module being created for all the editors to share.
The engine support the BPMN2 way, but the editors are not updated and sync at the same level yet, but as I mention they are working on it.
Cheers