After aborting or suspending a session, the SSM dies. Why is the session still open after the SSM recovers?

This situation can only happen if your session is recoverable. When you abort or suspend your recoverable session, the SSM has to update its persistent storage to indicate that the session has been aborted or suspended.

If the SSM crashes before it can update its persistent data, the session will be recovered and set to its previous state, which is OPEN.