Callkit - problems with Compact UI on iOS 14

In case of an incoming call to any VOIP app user now can ignore the call and go back to the home screen.

But in case the user decides to open the VOIP app with an incoming call he can answer it, but CallKit will remain in the ringing state.

What's the correct behavior? Should the app not allow answering through its UI? Or is there an API to tell CallKit that the user already answered the call?