What I didn't get from the video is that there's a differential, but it is not connected to the wheels. Is there a second differential that connects MG1 to the wheels?
The planetary gear works as a differential with the Sun gear, Planet carrier, and Ring gear each connected to something. You can see how this works here:
The planetary gear works as a differential with the Sun gear, Planet carrier, and Ring gear each connected to something. You can see how this works here:
https://eahart.com/prius/psd/