Voice Chat sound output from the wrong device

My active/default sound output device is the HyperX Cloud headset. I also have BenQ monitor speakers, but these are not active.

In Marathon, all in-game sounds, such as music, the UI, footsteps and gunshots, come from my active headset, while all voice chat sounds come from my inactive monitor speakers. I have never experienced this issue in any other game. Why does Marathon use my inactive device for voice output?