It's a voice-to-text-to-voice approach, as implied by this description:

"host transcription, LLM inference, and voice generation all together in one place"

I think there are some benefits to going through text rather than using a voice-to-voice model. It creates a 100% reliable paper trail of what the model heard and said in the conversation. This can be extremely important in some applications where you need to review and validate what was said.