Arrghh! Routers cannot take pipeline output as condition

After taking a look at the code and trying it out myself, I believe that pipelines are not as dynamic as the description leads me to. Specifically, the relevant documentation states:

  1. Dynamic Workflow: Adapt your pipeline’s behavior based on input characteristics or intermediate results.

I don’t see how an upstream sub-pipeline output can influence the downstream route chosen in a pipeline router. Can somebody correct me?