I'm still wondering what the docking looks like. Somehow people need to get from the connector cabin to the train and back. This could also result in a lot of people moving back and forth within the train over 20 stops if you can only get in and out at the back of it.
The route mentioned in the video has 30 stops over a distance of ~2200 km so it's unlikely there'd be much congestion. Stops here in Australia are even sparser over those sorts of distances so it'd work quite well here too.
maybe the connector cabin could move along the train and dock above every car. my main concerns are existing tunnels and the aerodynamic profile.