The documentation of output ports (cf. https://doc.akka.io/docs/akka/current/stream/stream-customize.html#port-states-and-) states that the initial state is marked green. That state would be “PULLED”. I think that this is wrong: the initial state is “PUSHED”.
Thanks for reporting. I think you are right. Amazing that it could have been wrong for so long without anyone noticing. Please create an issue in Github akka/akka.