Strategy that treats cancelStage the same as completeStage, i.e. all inlets are cancelled (propagating the cancellation cause) and all outlets are regularly completed.

This used to be the default behavior before Akka 2.6.

This behavior can be problematic in stacks of BidiFlows where different layers of the stack are both connected through inputs and outputs. In this case, an error in a doubly connected component triggers both a cancellation going upstream and an error going downstream. Since the stack might be connected to those components with inlets and outlets, a race starts whether the cancellation or the error arrives first. If the error arrives first, that's usually good because then the error can be propagated both on inlets and outlets. However, if the cancellation arrives first, the previous default behavior to complete the stage will lead other outputs to be completed regularly. The error which arrive late at the other hand will just be ignored (that connection will have been cancelled already and also the paths through which the error could propagates are already shut down).