In the video, did it actually do that though?
I saw a few close ups of some red moving parts, that might have done switching. But, it was hard to tell if they did switching, or were just part of the normal operation. The text didn't help me.
What I definitely saw were people getting out of one car, walking past an overhead sign for a new destination, getting in a new line and getting in a new car. With multiple lines all meeting in the same building. Which sounds exactly like what Disney is doing at the CBR Hub. I suppose the signs might be different, probably have icons/characters by the names.
I expect the Riviera station to be a passthrough that also allows boarding with no need to get off unless that's your destination. Presumably, the upstream station will send an empty car now and then if there's a line forming at Riviera. Simple communication between sites to request the empties, and only an issue at park open/close when there's extra demand. Plenty of empties in the middle of the day.