Android MediaRouter splitting audio and video routes to play video on external display via Presentation and audio via bluetooth

Question

I am writing an app that utilizes an external display (HDMI and/or wireless miracast or chromecast display) to play video in a Presentation via the DisplayManager

I am trying to force the audio from that video to play via a bluetooth a2dp profile if one is connected. I find the route info for the bluetooth device easily enough, and select it for the audio route:

        final MediaRouter mediaRouter = (MediaRouter) context.getSystemService(Context.MEDIA_ROUTER_SERVICE);
        int nRoutes = mediaRouter.getRouteCount();
        for (int i = 0; i < nRoutes; i++) {
            if (mediaRouter.getRouteAt(i).getDeviceType() == MediaRouter.RouteInfo.DEVICE_TYPE_BLUETOOTH) {
                mediaRouter.selectRoute(MediaRouter.ROUTE_TYPE_LIVE_AUDIO, mediaRouter.getRouteAt(i));
                break;
            }
        }

This works, BUT, it causes the wifi display to disconnect completely rather than continue to play the video. How can I tell android that I only want to override the audio route and not the video. Strangely, the RouteInfo object that has DEVICE_TYPE_BLUETOOTH indicates that it supports both ROUTE_TYPE_LIVE_AUDIO and ROUTE_TYPE_LIVE_VIDEO which doesn't seem right to me.