In the example task-jsf is a CDI Producer used to generate the FacesContext Injection Point from the static method reference.
@Produces public FacesContext getFacesContext()

The JSF docs say, the injection from FacesContext and ExternalContext should work out of the box. This does not work in the JBoss EAP 7.3

In my opinion it would be better and easier to understand if a concreate configuration class is used.

In the bug reported for JSF(see here) such a class is suggested.

@FacesConfig(version = Version.JSF_2_3) @ApplicationScoped public class Config {}

With this class the example works as designed and all JSF 2.3 features as well.