You're right that this example is broken. Putting that aside, all the @Validator annotation does for you is allow you to avoid declaring it in faces-config.xml. So it works just like any other JSF validator (in terms of validation).
Can you file a JIRA regarding this error?
Looks good to me.
Two things to remember around here. If they bite, bite back (it's play biting, so don't worry). Let your voice be heard. I have fought closed issues to get them reopened, so persistence is key.