!str #15604: Removal of default fanout

No, it is just the Outputs for the substreams. If you want to handle the substream outputs the "correct" way, then for example if you would have 6 substreams you would need to write subOut1.subreceive orElse subOut2.subreceive orElse subOut3.subreceive, etc. 

Instead the behavior of *all* substreams are handled in *one* receive block that dispatches on the key in the message. Since that means that the subreceive on the actual output *must not* be used since it would be a bug -- therefore it throws instead to make this clear.