Weird interface behaviour

In a libgdx project I realized that if you make the IOSMoeLauncher implement the delegate interface (in this case it is VungleSDKDelegate, binding generated with moe), you can see that callbacks work properly. On the other hand, if you create a class which implements the delegate interface and set its instance as delegate, callbacks do not work. What could be the reason?

Case 1 (working):

iOSMoeLauncher extends IOSApplication.Delegate implements VungleSDKDelegate{

vungleSDK.setDelegate(this);

@Override
@Selector(“vungleSDKDidInitialize”)
public void vungleSDKDidInitialize() {
System.out.println("VungleSDK initialized ");
}
}

Case 2 (callbacks do not work):

public class VungleSDKDelegateImpl implements VungleSDKDelegate {
@Override
@Selector(“vungleSDKDidInitialize”)
public void vungleSDKDidInitialize() {

}

}

iOSMoeLauncher extends IOSApplication.Delegate{

VungleSDKDelegateImpl delegate = new VungleSDKDelegateImpl();
vungleSDK.setDelegate(delegate);

}

Interesting that Case 2 works for UnityAds.