From the docs
It is not a general-purpose publish-subscribe system, nor is it intended for interprocess communication
What do they mean by saying it's not a general-purpose publish-subscribe system?
As far as I understand this is within a JVM only, publish/subscribe is usually between processes residing in potentially different places: like one JVM talking to another, suppose one Spring application publishing events that are to be consumed by another Spring application, residing in entirely different places.