The event bus in all these examples looks an awful lot like just a different name for a log, and adding an event bus has some minor downsides in that it require

The event bus in all these examples looks an awful lot like just a different name for a log, and adding an event bus has some minor downsides in that it requires more complex setup (with additional points of failure and points of difference between local and production deployment) and you would need to use special tooling to get the actual messages recorded somewhere and your hands on the contents of the messages when you need to debug. On the flipside the event bus messages may be useful for more than just human debugging. It's a shame the author didn't actually look at logging as a code smell. For example, is a high density of logging statements in code an indication of places which are brittle and hard to figure out and therefore candidates for reworking? That would be an interesting topic I think.