WTH can't I select my Android companion app as a satellite for Voice Assist?

I’ve just started experimenting with Voice Assist on my Android phone, and I’m eager to learn how to use it more effectively so I can make it a more central method of control. One thing that I particularly like are the voice options for TTS with Wyoming Piper. I’d really prefer using the same voice for all responses, if not just for consistency.
Am I missing something, or can we not choose our companion app as a satellite for TTS voice announcements (with Voice Assist Satellite announcements)? It seems like that should be a standard function since there will probably be many people that would like to use their old phones as “smart speakers”, or at least in conjunction with these old voice assistants (echos, etc.) using bluetooth.