When defining beans inheriting the following interface:

public interface ServiceRegistry<T> {
    void register(T service, Map<String, ?> properties);
    void unregister(T service, Map<String, ?> properties);
}

All service registrations makes the register method to be called twice.
It seems that the introspection on the class returns two methods, one with typed with Object, and another one typed with the actually class for T.
It seems the caller loops for all methods and call all of them. The documentation is not very clear about that, but I would think that only a single method for the given name would be called, and not all the versions of it.