I tried it and it is true. The solution is comment the code on servletDestroyed.
It is know JSF 2.0 spec section 5.4.1 says this:
"...Methods on managed beans declared to be in request, session, or application scope, annotated with @PreDestroy, must be called by the JSF implementation before the bean is removed from its scope or before the scope itself is destroyed, whichever comes first...."
Unfortunately, it is not possible to handle it on servletDestroyed first and then on attributeRemoved, because there is no way to know when the session object is being destroyed from the listener, so the best bet is let the code in just one place.