The current spec doesn't define what should happen if a CDI bean @Specializes a session bean, e.g.

@Stateless
public class Horse

{..}

@ApplicationScoped @Specializes
public class Trakehner extends Horse {..}

Section 3.2.4 explicitely forbids the other way around. I think we should also treat the above case as error.
Otherwise we would end up getting different results whether we use @Inject or @EJB to inject a Horse.