Given that, my take is that:

1. Our biggest risk of confusion would be to have the the spec be inconsistent between these cases.
2. The behavior specified for actionListener (event parameter is optional) is the preferred behavior.  (We intentionally added this behavior in 2.0)
3. The fact that Mojarra implements this behavior for f:event's listener attribute as well is a good thing (and probably intentional).
4. We should update the spec in our upcoming MR to clarify that the current behavior is by design.

I have logged the following spec issue to track this:

https://javaserverfaces-spec-public.dev.java.net/issues/show_bug.cgi?id=731

Andy

The reason you want to make it so is to have a better unit testing story.

Cay