FaceTime (Mac) Video Menu Output/Microphone Not Working

When I use FaceTime on my mac (El Capitan 10.11.5) the audio input/output for the FaceTime call uses the Sound settings in System Preferences but not the settings in the FaceTime -> Video menu -> Output/Microphone options. So if I have music playing through the internal speakers but want the FaceTime call to route through a set of USB-attached headphones, the settings in the Video menu are ignored and the FaceTime call is routed through whatever is set in System Preferences.

Does anyone else have this problem?

Am I not understanding the purpose of the Video menu settings in FaceTime?

Any help is appreciated.