H Maciej,
I think the point is whether we should achieve the discriminator design pattern. In discriminator design pattern, the join node will end split executions when they arrived join node, it do not terminate them while the first of execution arrived join node.
Indeed, it will increase the complex level of implements. So I think we could terminate all other executions in jBPM 4.4. And think about other scenarios in the future.
By the way, I had met the wrong behaviour you mentained. There were two managers in a department. When a contact arrived, both of them need review it. But if one of them is off the office, the process should not wait, the process will continue to the next step when one of them review it. And if the other manager come back, he need review the contact again and let the process go to next step again.
In my opinion, this process is totally strange, so we neednot achieve it in jPDL. :)