CDI 1.0 11.5.2. AfterBeanDiscovery event states:
"addObserverMethod() fires an event of type ProcessObserverMethod containing the given ObserverMethod and then registers the ObserverMethod with the container, thereby making it available for event."

No event of type ProcessObserverMethod is fired when adding new observer method via javax.enterprise.inject.spi.AfterBeanDiscovery.addObserverMethod(ObserverMethod<?>). However the new observer method is registered correctly. Refer to CDI TCK test [1].

[1] https://github.com/jboss/cdi-tck/blob/master/impl/src/main/java/org/jboss/jsr299/tck/tests/extensions/afterBeanDiscovery/AfterBeanDiscoveryTest.java