Can I use @XmlElementWrapper on web service operations?

Issue

I have an EJB3 that expose webMethod defined as follows

@WebService
@Stateless
public class CalcEJB3Bean implements CalcEJB3 {

 @XmlElementWrapper
    public List<CalcArgs> echoArgsList( List<CalcArgs> args) {
        return args;
   }
}

The return value is wrapped as expected but not the call argument. The specification says that this annotation can be applied on methods and its purpose is :

"Generates a wrapper element around XML representation. This is primarily intended to be used to produce a wrapper XML element around collections"

Why does it apply only on return value but not on arguments of type Collection?