Facetime will not use the midi multi output device setting for internal speakers and headset

I have setup a midi multi output device with internal speakers and a headset. But Facetime doesn't want to output to both the internal speakers and headset. It's one or the other. This configuration works fine with Skype. Is there another setting in FaceTime that has to be setup?

iMac 27inch 2017 with mac OS Monterey 12.6.

I have a tried this on a Ventura OS and it doesn't work there either. I have different headsets in the multi output setup and that doesn't work.

Any ideas? Or is this just broken in the Mac OS to FaceTime interface?